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HASKELL  F.   NORMAN 


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BIOLOGICAL  LECTURES  ""'•'" 


DELIVERED  AT 


THE    MARINE    BIOLOGICAL    LABORATORY 
OF    WOOD'S    HOLL 


In  the  Summer  Session  of  189? 


A 

^ 

< 

•^'• 

>^" 

BOSfip^,   U.S.A. 

PUBLISHED    BY   GINN   & 

COMPANY 

1894 

By  GINN   &  COMPANY. 


ALL   RIGHTS    RESERVED. 


PREFACE. 


In  offering  the  second  volume  of  these  lectures,^  it  may  be 
well  to  remind  the  reader  who  may  not  be  acquainted  with  the 
Laboratory,  that  only  one  side  of  our  work  is  here  represented. 
Such  a  series  of  lectures  on  special  problems  in  biology  is 
offered  every  summer;  but  the  main  body  of  our  lectures 
is  of  quite  a  different  type,  having  direct  reference  to  the 
instruction  going  on  in  the  laboratories.  As  a  rule,  these 
special  lectures  are  given  by  investigators,  who  undertake  not 
only  to  review  the  field,  but  also  to  set  forth  the  results  of  their 
own  work.  While  these  lectures  may  show  the  general  drift 
of  the  authors'  investigations,  they  cannot,  of  course,  be  ex- 
pected to  give  a  complete  account  of  the  facts  on  which  the 
conclusions  are  based.  In  lectures  of  this  kind  due  allowance 
must  be  made  for  the  authors'  limitations  in  time,  as  the  sub- 
ject is  often  one  which  would  require  a  dozen  or  more  lectures 
for  its  complete  elaboration.  Somewhat  greater  freedom  in  the 
expression  of  opinion  than  might  be  expected  in  strictly  scientific 
communications,  must  also  be  permitted.  In  fact,  it  is  one  of 
the  leading  objects  of  this  course  of  lectures  to  bring  forward  the 
unsettled  problems  of  the  day,  and  to  discuss  them  freely.  It  is 
to  be  expected,  of  course,  that  now  and  then  opposed  stand- 
points will  be  developed,  as  has  happened  this  time;  but  these 
differences  exist,  and  will  continue  to  exist,  as  long  as  anything 
remains  for  investigation,  and  the  scientific  reader  will  not  be 
surprised  to  find  them  here.  It  may  be  hardly  necessary  to 
add  that  the  authors  are  severally  responsible  for  the  method 
and  form  of  their  lectures.  A  brief  account  of  the  work  and 
aims  of  the  Laboratory  will  be  found  in  the  appendix. 

C.  O.  Whitman. 

1  The  first  volume  appeared  in  1890. 


CONTENTS. 


LECTURE  PAGE 

I.     The  Mosaic  Theory  of  Development.  E.B.Wilson.  i 

II.     TJie  Fertilization  of  the  Ovum.     E.  G.  Conklin  .  15 

III.  Oil  Soine  Facts  and   Principles  of  Physiological 

Morphology.     J.  Loeb 37 

IV.  Dynamics  in  Evolution.     J.  A.  Ryder    ....  63 

V.     On  the  Nature  of  Cell  Organization.    S.  Watase  .  83 

VI.     TJie  Inadequacy  of  the  Cell-  Theory  of  Development. 

C.  O.  Whitman 105 

VII.    Bdellostoma  Dombeyi,  Lac.     Howard  Ayers  .     .  125 

VIII.     The    hifltcence   of  External    Coiiditions  on  Plant 

Life.     W.   P.  Wilson 163 

IX.    Irrito-Contractility  in  Plaiits.     J.  Muirhead  Mac- 

FARLANE 1 85 

X.     The  Marine  Biological  Stations  of  Europe.    Bash- 
ford  Dean 211 

Appendix —  TJie  Work  and  the  Aims  of  the  Ma- 
rine Biological  Laboratory .     CO.  Whitman.  235 


FIRST  LECTURE. 

THE  MOSAIC  THEORY  OF  DEVELOPMENT. 

EDMUND    B.    WILSON. 

A  REMARKABLE  awakening  of  interest  and  change  of  opinion 
has  of  late  taken  place  among  working  embryologists  in  regard 
to  the  cleavage  of  the  ovum.  So  long  as  the  study  of  embry- 
ology was  dominated  by  the  so-called  biogenetic  law,  so  long 
as  the  main  motive  of  investigation  was  the  search  for  phyletic 
relationships  and  the  construction  of  systems  of  classification, 
the  earlier  stages  of  development  were  little  heeded.  The 
two-layered  gastrula  was  for  the  most  part  taken  as  the  real 
starting-point  for  research,  and  the  segmentation  stages  were 
briefly  dismissed  as  having  little  purport  for  the  more  serious 
problems  involved  in  the  investigation  of  later  stages.  The 
cleavage  is  equal  or  unequal,  total  or  partial,  regular  or  irregular; 
the  diblastic  condition  attained  by  delamination,  migration  or 
invagination  ;  the  gastrulation  embolic  or  epibolic  :  —  such 
were  the  general  conclusions  announced  regarding  the  prae- 
gastrular  stages  in  a  large  proportion  of  the  embryological 
papers  published  down  to  the  time  of  Balfour  and  even  later. 
The  last  decade  has,  however,  witnessed  so  extraordinary  a 
change  of  front  on  this  subject  that  it  will  not  be  out  of  place 
to  review  briefly  the  three  leading  causes  by  which  it  has  been 
brought  to  pass. 

First,  it  has  become  more  and  more  clear  that  the  germ-layer 
theory  is,  to  a  certain  extent,  inadequate  and  misleading,  and 
that  even  the  primary  layers  of  the  "gastrula"  cannot  be 
regarded  as  strictly  homologous  throughout  the  animal  kingdom. 
To  assume  that  they  are  so  involves  us  in  inextricable  difficul- 
ties —  such  as  those  for  instance  encountered  in  the  comparison 
of  the  annelid  gastrula  with  that  of  the  chordates,  or  the  com- 


2  BIOLOGICAL   LECTURES. 

parison  of  the  sexual  and  asexual  modes  of  development  in 
tunicates,  bryozoa,  worms  and  coelenterates.  This  considera- 
tion led  some  morphologists  to  insist  on  the  need  of  a  more 
precise  investigation  of  the  prae-gastrular  stages,  and  the  desi- 
rability of  taking  as  a  starting-point  not  the  two-layered  gastrula 
but  the  undivided  ovum.  ''The  'gastrula'  cannot  be  taken  as 
a  starting-point  for  the  investigation  of  comparative  organo- 
geny unless  we  are  certain  that  the  two  layers  are  everywhere 
homologous.  Simply  to  assume  this  homology  is  simply  to 
beg  the  question.  The  relationsJiip  of  the  inner  and  outer 
layei^s  in  the  variojis  forms  of  gastrnlas  nmst  be  investigated 
not  only  by  determining  their  relationsJiip  to  the  adult  body,  but 
also  by  tracing  out  the  cell-lineage  or  cytogeny  of  the  individttal 
blastomcres  from  the  begifuiing  of  development .'' 

The  second  of  the  causes  referred  to  was  the  discovery  of  the 
so-called  pro-morphological  relations  of  the  segmenting  ovum. 
It  is  now  just  ten  years  since  Roux  and  Pfliiger  independently 
announced  the  discovery  that  the  first  plane  of  cleavage  in  the 
frog's  Qgg  coincides  with  the  median  plane  of  the  adult  body 
(a  fact  announced  many  years  earlier  by  Newport,  whose  obser- 
vation fell,  however,  into  oblivion).  The  same  result  was  soon 
afterwards  reached  in  the  case  of  the  cephalopod  (Watase)  and 
tunicate  (Van  Benden  and  Julin),  and  for  a  time  it  seemed  not 
improbable  that  a  general  law  had  been  determined.  Later 
researches  disappointed  this  expectation  ;  for  it  was  demon- 
strated that  the  first  cleavage  plane  may  be  transverse  to  the 
body  (annelids,  gasteropods,  urodeles),  or  even  in  some  cases 
show  a  purely  variable  and  inconstant  relation  (teleosts). 
The  fact  remained,  however,  that  in  the  greater  number  of 
known  cases  definite  relations  of  symmetry  can  be  made  out 
between  the  early  cleavage  stages  and  the  adult  body  ;  and 
this  fact  invested  these  stages  with  a  new  and  captivating 
interest. 

The  third  and  most  important  cause  lay  in  the  new  and 
startling  results  attained  by  the  application  of  experimental 
methods  to  embryological  study,  and  especially  to  the  investi- 
gation of  cleavage.  The  initial  impulse  in  this  direction  was 
given  in  1883  by  the  investigations  of  Pfliiger  upon  the  influ- 


THE   MOSAIC   THEORY  OF  DEVELOPMENT.  3 

ence  of  gravity  and  mechanical  pressure  upon  the  segmenting 
ova  of  the  frog.  These  pioneer  studies  formed  the  starting- 
point  for  a  series  of  remarkable  researches  by  Roux,  Driesch, 
Born  and  others,  that  have  absorbed  a  large  share  of  interest 
on  the  part  of  morphologists  and  physiologists  alike  ;  and  it 
is  perhaps  not  too  much  to  say  that  at  the  present  day  the 
questions  raised  by  these  experimental  researches  on  cleavage 
stand  foremost  in  the  arena  of  biological  discussion,  and  have 
for  the  time  being  thrown  into  the  background  many  problems 
which  were  but  yesterday  generally  regarded  as  the  burning 
questions  of  the  time.  It  is  the  purpose  of  this  lecture  to 
consider,  briefly,  the  most  central  and  fundamental  subject  of 
the  current  controversy. 

It  is  an  interesting  illustration  of  how  even  scientific  history 
repeats  itself  that  the  leading  issue  of  to-day  has  many  points 
of  similarity  to  that  raised  two  hundred  years  ago  between  the 
prae-formationists  and  the  epigenesists.  Many  leading  biolo- 
gical thinkers  now  find  themselves  compelled  to  accept  a  view 
that  has  somewhat  in  common  with  the  theory  of  prse-forma- 
tion,  though  differing  radically  from  its  early  form  as  held  by 
Bonnet  and  other  evolutionists  of  the  eighteenth  century.  No 
one  would  now  maintain  the  archaic  view  that  the  embryo 
prae-exists  as  such  in  the  ovum.  Every  one  of  its  hereditary 
characters  is,  however,  believed  to  be  represented  by  definite 
structural  units  in  the  idioplasm  of  the  germ-cell,  which  is 
therefore  conceived  as  a  kind  of  microcosm,  not  similar  to, 
but  a  perfect  symbol  of,  the  macrocosm  to  which  it  gives  rise 
(Hertwig).  In  its  modern  form  this  doctrine  was  first  clearly 
set  forth  by  Darwin  in  the  theory  of  Pangenesis  ('68).  Twenty 
years  later  ('89)  it  was  remodeled  and  given  new  life  by  Hugo 
de  Vries,  in  a  profoundly  interesting  treatise  entitled  Intra- 
celhdar  Pangenesis  and  in  its  new  form  was  accepted  by 
Oscar  Hertwig,  and  pushed  to  its  uttermost  logical  limit  by 
Weismann.  Kindred  theories  have  been  maintained  by  many 
other  leading  naturalists. 

The  considerations  which  have  led  to  the  rehabilitation  of 
4    the  theory  of   pangenesis  are  based  upon  the  facts  of  what 


2  BIOLOGICAL   LECTURES. 

parison  of  the  sexual  and  asexual  modes  of  development  in 
tunicates,  bryozoa,  worms  and  coelenterates.  This  considera- 
tion led  some  morphologists  to  insist  on  the  need  of  a  more 
precise  investigation  of  the  prae-gastrular  stages,  and  the  desi- 
rability of  taking  as  a  starting-point  not  the  two-layered  gastrula 
but  the  undivided  ovum.  ''The  'gastrula'  cannot  be  taken  as 
a  starting-point  for  the  investigation  of  comparative  organo- 
geny unless  we  are  certain  that  the  two  layers  are  everywhere 
homologous.  Simply  to  assume  this  homology  is  simply  to 
beg  the  question.  The  relationship  of  the  i^itier  and  onter 
layers  in  the  various  forms  of  gastridas  must  be  investigated 
not  only  by  determining  their  relationship  to  the  adult  body,  but 
also  by  tracing  out  the  cell-lineage  or  cytogeny  of  the  individual 
blastomeres  from  the  begijiniftg  of  development.'' 

The  second  of  the  causes  referred  to  was  the  discovery  of  the 
so-called  pro-morphological  relations  of  the  segmenting  ovum. 
It  is  now  just  ten  years  since  Roux  and  Pfliiger  independently 
announced  the  discovery  that  the  first  plane  of  cleavage  in  the 
frog's  Qgg  coincides  with  the  median  plane  of  the  adult  body 
(a  fact  announced  many  years  earlier  by  Newport,  whose  obser- 
vation fell,  however,  into  oblivion).  The  same  result  was  soon 
afterwards  reached  in  the  case  of  the  cephalopod  (Watase)  and 
tunicate  (Van  Benden  and  Julin),  and  for  a  time  it  seemed  not 
improbable  that  a  general  law  had  been  determined.  Later 
researches  disappointed  this  expectation;  for  it  was  demon- 
strated that  the  first  cleavage  plane  may  be  transverse  to  the 
body  (annelids,  gasteropods,  urodeles),  or  even  in  some  cases 
show  a  purely  variable  and  inconstant  relation  (teleosts). 
The  fact  remained,  however,  that  in  the  greater  number  of 
known  cases  definite  relations  of  symmetry  can  be  made  out 
between  the  early  cleavage  stages  and  the  adult  body  ;  and 
this  fact  invested  these  stages  with  a  new  and  captivating 
interest. 

The  third  and  most  important  cause  lay  in  the  new  and 
startling  results  attained  by  the  application  of  experimental 
methods  to  embryological  study,  and  especially  to  the  investi- 
gation of  cleavage.  The  initial  impulse  in  this  direction  was 
given  in  1883  by  the  investigations  of  Pfluger  upon  the  influ- 


THE  MOSAIC   THEORY  OF  DEVELOPMENT  3 

ence  of  gravity  and  mechanical  pressure  upon  the  segmenting 
ova  of  the  frog.  These  pioneer  studies  formed  the  starting- 
point  for  a  series  of  remarkable  researches  by  Roux,  Driesch, 
Born  and  others,  that  have  absorbed  a  large  share  of  interest 
on  the  part  of  morphologists  and  physiologists  alike  ;  and  it 
is  perhaps  not  too  much  to  say  that  at  the  present  day  the 
questions  raised  by  these  experimental  researches  on  cleavage 
stand  foremost  in  the  arena  of  biological  discussion,  and  have 
for  the  time  being  thrown  into  the  background  many  problems 
which  were  but  yesterday  generally  regarded  as  the  burning 
questions  of  the  time.  It  is  the  purpose  of  this  lecture  to 
consider,  briefly,  the  most  central  and  fundamental  subject  of 
the  current  controversy. 

It  is  an  interesting  illustration  of  how  even  scientific  history 
repeats  itself  that  the  leading  issue  of  to-day  has  many  points 
of  similarity  to  that  raised  two  hundred  years  ago  between  the 
prae-formationists  and  the  epigenesists.  Many  leading  biolo- 
gical thinkers  now  find  themselves  compelled  to  accept  a  view 
that  has  somewhat  in  common  with  the  theory  of  prse-forma- 
tion,  though  differing  radically  from  its  early  form  as  held  by 
Bonnet  and  other  evolutionists  of  the  eighteenth  century.  No 
one  would  now  maintain  the  archaic  view  that  the  embryo 
prae-exists  as  stick  in  the  ovum.  Every  one  of  its  hereditary 
characters  is,  however,  believed  to  be  represented  by  definite 
structural  units  in  the  idioplasm  of  the  germ-cell,  which  is 
therefore  conceived  as  a  kind  of  microcosm,  not  similar  to, 
but  a  perfect  symbol  of,  the  macrocosm  to  which  it  gives  rise 
(Hertwig).  In  its  modern  form  this  doctrine  was  first  clearly 
set  forth  by  Darwin  in  the  theory  of  Pangenesis  ('68).  Twenty 
years  later  ('89)  it  was  remodeled  and  given  new  life  by  Hugo 
de  Vries,  in  a  profoundly  interesting  treatise  entitled  Iiitra- 
celhdar  Pangenesis  and  in  its  new  form  was  accepted  by 
Oscar  Hertwig,  and  pushed  to  its  uttermost  logical  limit  by 
Weismann.  Kindred  theories  have  been  maintained  by  many 
other  leading  naturalists. 

The  considerations  which  have  led  to  the  rehabilitation  of 
4    the  theory  of   pangenesis  are  based  upon  the  facts  of  what 


4  BIOLOGICAL  LECTURES. 

Gallon  has  called  particulate  inheritance.  The  phenomena  of 
atavism,  the  characters  of  hybrids,  the  facts  of  spontaneous 
variation,  all  show  that  even  the  most  minute  characteristics 
may  independently  appear  or  disappear,  may  independently 
vary,  and  may  independently  be  inherited  from  either  parent 
without  in  any  way  disturbing  the  equilibrium  of  the  organ- 
ism, or  showing  any  correlation  with  other  variations.  These 
facts,  it  is  argued,  compel  the  belief  that  hereditary  character- 
istics are  represented  in  the  idioplasm  by  distinct  and  definite 
germs  ( "  pangens,"  **  idioblasts,"  ''biophores,"  etc),  which 
may  vary,  appear  or  disappear,  become  active  or  latent,  without 
affecting  the  general  architecture  of  the  substance  of  which 
they  form  a  part.  Under  any  other  theory  we  must  suppose 
variations  to  be  caused  by  changes  in  the  molecular  composi- 
tion of  the  idioplasm  as  a  whole,  and  no  writer  has  shown, 
even  in  the  most  approximate  manner,  how  inarticulate  inheri- 
tance can  thus  be  conceived. 

Based  upon  this  conception  two  radically  different  theories 
of  development  have  recently  been  propounded.  The  first  of 
these  —  the  so-called  mosaic  theory  of  Roux  and  Weismann, 
which  forms  the  subject  of  this  lecture  —  is  based  upon  the 
assumption  that  the  cause  of  differentiation  lies  in  the  nature 
of  cell-division.  Karyokinesis  is  conceived  as  qualitative  in 
character  in  such  wise  that  the  idioplasmic  germs  are  sifted 
apart,  and  cells  of  different  prospective  values  receive  their 
appropriate  specific  germs  at  the  moment  of  their  forma- 
tion. The  idioplasm  therefore  becomes  progressively  simpler 
as  the  ontogeny  goes  forward,  except  in  the  case  of  the  germ- 
cells  ;  these  retain  a  store  of  the  original  mixture  (''germ- 
plasm"  of  Weismann).  Every  cell  must  therefore  possess  an 
independent  power  of  self-determination  inherent  in  the  specific 
structure  of  its  idioplasm,  and  the  entire  ontogeny  is  aptly 
compared  by  Roux  to  a  mosaic-work  ;  it  is  essentially  a  whole 
arising  from  a  number  of  independent  self-determining  parts, 
though  Roux  qualifies  this  conception  by  the  admission  that 
the  self-determining  power  of  the  cell  is  capable  in  some 
measure,  of  modification,  through  interaction  with  its  fellows 
(  "  correlative  differentiation  "  ). 


THE  MOSAIC    THEORY  OF  DEVELOPMENT  5 

In  the  hands  of  Weismann  this  theory  attains  truly  colossal 
proportions.  The  primary  germs  or  units  (which  he  calls 
'*  biophores " )  are  aggregated  to  form  ''determinants,"  the 
determinants  to  form  "ids,"  and  the  ids  to  form  "idants," 
which  are  identified  with  the  chromosomes  of  the  ordinary 
karyokinetic  figure.  Upon  this  basis  is  reared  a  stately  group 
of  theories  relating  to  reproduction,  variation,  inheritance  and 
regeneration,  which  are  boldly  pushed  to  their  utmost  logical 
limit.  These  theories  await  the  judgment  of  the  future. 
Brilliantly  elaborated  and  persuasively  presented  as  they  are, 
they  do  not  at  present,  I  believe,  carry  conviction  to  the  minds 
of  most  naturalists,  but  arouse  a  feeling  of  scepticism  and 
uncertainty;  for  the  fine-spun  thread  of  theory  leads  us  little 
by  little  into  an  unknown  region,  so  remote  from  the  terra  firma 
of  observed  fact  that  verification  and  disproof  are  alike  impos- 
sible. 

In  its  original  form  the  mosaic  theory  has,  I  believe,  received 
its  death-blow  from  the  facts  of  experimental  embryology, 
though  both  Roux  and  Weismann  still  endeavor  to  maintain 
their  position.  It  is  rather  curious  that  the  very  line  of 
research  struck  out  by  Roux,  by  which  he  was  led  to  the 
mosaic  theory,  should  in  later  years  have  ended  in  a  view  dia- 
metrically opposed  to  his  own.  In  1888  Roux  succeeded  in 
killing  (by  puncture  with  a  heated  needle)  one  of  the  first  two 
blastomeres  of  the  segmenting  frog's  ^^g.  The  uninjured 
blastomere  continued  its  development  as  if  still  forming  a  part 
of  an  entire  embryo,  giving  rise  successively  to  a  half-blastula, 
half-gastrula,  and  half-tadpole  embryo,  with  a  single  medullary 
fold.  Analogous  results  were  reached  by  operation  upon  four- 
celled  stages.  It  was  this  result  that  led  Roux  to  compare  the 
development  to  a  mosaic-work,  asserting  that  ''  the  development 
of  the  frog-gastrula,  and  of  the  embryo  immediately  derived 
from  it  is,  from  the  second  cleavage  onward,  a  mosaic-work, 
consisting  of  at  least  four  vertical  independently  developing 
pieces."  Roux  himself,  however,  showed  that  in  later  stages 
the  missing  half  (or  fourth)  is  perfectly  restored  by  a  process 
of  ''post-generation,"  which  begins  about  the  time  of  the 
formation  of  the  medullary  folds  —  a  result  which,   in   itself, 


6  BIOLOGICAL   LECTURES. 

really  contradicts  the  mosaic  hypothesis  ;  for  the  course  of 
events  in  the  uninjured  blastomere,  or  its  products,  is  radically 
altered  by  changes  on  the  other  side  of  the  embryo. 

A  more  decisive  result  was  reached  in  1891  by  Driesch,  who 
succeeded,  in  the  case  of  EcJiinns,  in  effecting  a  complete  sepa- 
ration of  the  blastomeres  by  shaking  them  apart.  A  blastomere 
of  the  2-celled  stage,  thus  isolated,  gave  rise  to  a  perfect  but 
half-sized  blastula,  gastrula,  and  Pluteus  larva ;  an  isolated 
blastomere  of  the  4-celled  stage  produced  a  perfect  dwarf  gas- 
trula one-fourth  the  normal  size.  Even  in  this  case,  however, 
the  earliest  stages  of  development  (cleavage)  showed  traces  of 
the  normal  development,  the  isolated  blastomere  segmenting, 
as  if  it  were  a  half-embryo,  and  only  becoming  a  perfect  whole 
in  the  blastula  stage.  In  the  following  year,  however,  the 
writer  repeated  Driesch's  experiments  in  the  case  of  AinpJii- 
oxtis  (the  Qgg  of  which  is  extremely  favorable  for  experiment), 
and  found  that  in  this  case  there  is,  as  a  rule,  no  preliminary 
half-development  whatever.  The  isolated  blastomere  behaves 
from  the  beginning  like  an  entire  ovum  of  one-half  or  one- 
fourth  the  normal  size. 

It  is  quite  clear  that  in  Amphioxus  the  first  two  divisions  of 
the  ovum  are  not  qualitative,  as  the  mosaic  theory  assumes, 
but  purely  quantitative  ;  for  the  fact  that  each  of  the  two  or 
four  blastomeres  may  give  rise  to  a  perfect  gastrula  proves  that 
all  contain  the  same  materials.  Nevertheless,  in  the  normal 
development,  these  cells  give  rise  to  different  structures  —  i.  e., 
they  have  a  different  prospective  value  —  from  which  it  follows 
that,  in  this  case  at  least,  differentiation  is  not  caused  by  quali- 
tative cell-division,  but  by  the  conditions  under  which  the  cell 
develops. 

These  facts  are  obviously  a  serious  blow  to  the  mosaic 
theory,  and  the  efforts  of  Roux  and  Weismann  to  sustain  their 
hypothesis  in  the  face  of  such  evidence  only  serve  to  emphasize 
the  weakness  of  their  case.  In  order  to  explain  the  facts  of 
post-generation  —  i.e.,  the  capability  of  isolated  blastomeres 
to  produce  complete  embryos  —  both  Roux  and  Weismann  are 
compelled  to  set  up  a  subsidiary  hypothesis,  assuming  that 
during  cell-division   each   cell  may  receive,  in  addition   to  its 


THE   MOSAIC    THEORY   OF  DEVELOPMENT.  7 

specific  form  of  idioplasm,  a  portion  of  unmodified  idioplasm 
afforded  by  purely  quantitative  division.  This  unmodified 
idioplasm  ("accessory  idioplasm"  of  Weismann,  or  in  some 
cases  "germ-plasm";  "post-generation  or  regeneration  idio- 
plasm "  of  Roux)  remains  latent  in  normal  development  which 
is  controlled  by  the  active  specific  idioplasm.  Injury  to  the 
ovum  —  e.  g.y  mechanical  separation  of  the  blastomeres  —  acts 
as  a  stimulus  to  the  latent  idioplasm,  which  thereupon  becomes 
active,  and  causes  a  repetition  of  the  original  development. 
By  assuming  a  variable  latent  period  following  the  stimulus, 
Roux  is  able  to  explain  the  fact  that  regeneration  takes  place 
at  different  periods  in  different  animals. 

Considered  as  a  purely  formal  explanation  this  subsidiary 
hypothesis  is  perfectly  logical  and  complete.  A  little  reflection 
will  show,  however,  that  it  really  abandons  the  entire  mosaic 
position,  by  rendering  the  assumption  of  qualitative  division 
superfluous;  and,  aside  from  this,  its  forced  and  artificial  char- 
acter, places  a  strain  upon  the  mosaic  theory  under  which  it 
breaks  down.  Both  of  the  two  fundamental  postulates  of  the 
modified  theory —  viz.^  qualitative  nuclear  division,  and  accessory 
latent  idioplasm  —  are  purely  imaginary.  They  are  complicated 
assumptions  in  regard  to  phenomena  of  which  we  are  really 
quite  ignorant,  and  they  lie  at  present  beyond  the  reach  of 
investigation.  The  "explanation"  is,  therefore,  unreal;  it 
carries  no  conviction,  and  no  real  explanation  will  be  possible 
until  we  possess  more  certain  knowledge  regarding  the  seat  of 
the  idioplasm  (which  is  entirely  an  open  question),  and  its 
internal  composition  and  mode  of  action  (which  is  wholly 
unknown).  In  the  meantime  we  certainly  are  not  bound  to 
accept  an  artificial  explanation  like  that  of  Roux,  however 
logical  and  complete,  unless  it  can  be  shown  that  the  phenomena 
are  not  conceivable  in  any  other  way. 

We  turn  now  to  a  brief  consideration  of  opposing  views, 
among  which  I  ask  attention  especially  to  those  of  Driesch  and 
Hertwig.  In  common  with  Kolliker  and  many  other  eminent 
authorities,  these  authors  insist  that  cell  division  is  not  quali- 
tative but  quantitative  only,  and  hence  is  not,  /rr  sc,  a  cause 


lO  BIOLOGICAL  LECTURES. 

we  find,  for  example,  among  the  annelids;  and  I  would  ask 
attention  for  a  moment  to  the  case  of  Nereis,  which  is,  at 
present,  the  best  known  form.  Differentiation  here  begins  at 
the  very  first  cleavage  (which  is  conspicuously  unequal),  and 
it  becomes  more  pronounced  with  every  succeeding  division. 
The  median  plane  is  marked  out  at  the  second  cleavage  ;  at 
the  third  the  entire  ectoblast  of  the  trochal  and  prse-trochal 
regions  is  formed  ;  at  the  fourth  the  material  for  the  entire 
''ventral  plate  "  (including  the  ventral  nerve-cord  and  the  seta- 
sacs)  is  segregated  in  a  single  cell,  that  for  the  stomodaeum  in 
three  cells*;  the  fifth  cleavage  completes  the  ectoblast,  and  by 
the  38-celled  stage  the  germ-layers  are  completely  segregated 
(the  mesoblast  in  a  single  cell)  and  the  architecture  of  the 
embryo  is  fully  outlined  in  the  arrangement  of  the  parent 
blastomeres,  or  protoblasts. 

We  do  not  know  whether,  in  this  case,  the  first  two  blasto- 
meres are  qualitatively  different,  though  there  may  be  some 
ground  for  holding  that  they  are,  from  the  fact  that  the  larger 
of  the  two  contains  a  relatively  larger  proportion  of  protoplasm 
than  the  smaller.^  But  in  any  case  their  difference  in  size 
renders  it  impossible  that  they  should  play  interchangeable 
parts  in  the  cleavage.  The  entire  later  development  is,  how- 
ever, moulded  upon  the  2-celled  stage,  every  blastomere  having 
a  definite  relation  to  it  and  a  definite  morphological  value.  The 
development  is  a  visible  mosaic-work,  not  one  ideally  conceived 
by  a  mental  projection  of  the  adult  characteristics  back  upon 
the  cleavage  stages.  The  principle  of  ''organbildende  Keim- 
bezirke  "  has  here  a  real  meaning  and  value,  and  this  would 
remain  true  even  if  it  should  hereafter  be  shown  that  both  of 
the  first  two  blastomeres  of  Nereis,  if  isolated,  could  produce  a 
perfect  embryo. 

It  is  clear,  from  such  a  case,  that  the  more  extreme  views 
of  Driesch  and  Hertwig  cannot  be  accepted  without  consider- 
able modification.  It  seems  to  me,  however,  that  they  may  be 
modified  in  such  a  way  as,  without  sacrificing  the  principle  of 
epigenesis  for  which  they  contend,  to   recognize  certain   ele- 

1  All  my  attempts  to  separate  these  blastomeres  by  shaking  have  thus  far  been 
unsuccessful. 


THE   MOSAIC    THEORY  OF  DEVELOPMENT.  \\ 

ments  of  truth  in  the  mosaic  hypothesis  ;  and  I  will  attempt 
to  indicate  this  modification  by  a  comparison  between  Amphi- 
oxtis  and  Nereis.  In  the  case  of  AinpJiioxiis  we  have  the  clear- 
est evidence  that  differentiation  is,  in  a  measure,  dependent 
upon  the  relation  of  the  cell  to  the  whole  of  which  it  forms  a 
part.  The  first  visible  differentiation  in  this  case  is  at  the 
third  cleavage,  which  consists  in  an  unequal  division  of  each 
of  the  four  blastomeres,  so  as  to  give  rise  to  four  micromeres 
and  four  macromeres,  the  former  giving  rise  to  ectoblast  only, 
while  the  latter  give  rise  to  entoblast 
and  mesoblast  as  well  {Diagravi  I). 
If,  however,  the  blastomeres  of  the 
4-celled  stage  be  separated  (shaken 
apart)  the  course  of  events  is  entirely 
changed  ;  for  in  this  case  each  divides 
equally,  not  unequally,  and  ultimately 
gives  rise  to  a  complete  quarter-sized  ""    dlIgram  I. 

dwarf,    instead    of    one-quarter    of    a 

normal  embryo,  as  it  would  have  done  under  ordinary  cir- 
cumstances. The  character  of  the  fourth  cleavage  is  here 
directly  or  indirectly  determined  in  each  cell  by  the  relation 
of  the  cell  to  its  fellows  ;  and  if  this  is  true  of  any  one 
stage  of  the  ontogeny,  a  very  strong  presumption  is  created 
that  it  is  true  of  all  —  that,  in  the  process  of  progressive 
differentiation  occurring  in  the  course  of  every  animal  on- 
togeny, the  character  of  each  step  is  determined  by  the 
condition  of  the  entire  organism.  The  ontogeny  is,  in  other 
words,  a  connected  series  of  interactions  between  the 
various  parts  of  the  embryo,  in  which  each  step  estab- 
lishes new  relations,  through  which  the  following  step  is 
determined.  The  character  of  the  series,  as  a  whole,  depends 
upon  the  first  step,  and  this  in  turn  upon  the  constitution  of  the 
original  ovum.  In  Aniphioxiis  differentiation  proceeds  slowly, 
the  earlier  blastomeres  show  no  appreciable  divergence,  and  the 
first  stages  show  no  trace  of  a  mosaic  work.  In  Nereis,  on  the 
other  hand,  a  mosaic-like  character  appears  from  the  begin- 
ning, because  of  the  inequality  of  the  first  cleavage,  which 
conditions    the    entire    subsequent   development    through    the 


12 


BIOLOGICAL   LECTURES. 


peculiar  relations  established  by  it.  The  cause  of  the  inequa- 
lity must  lie  in  the  undivided  ovum,  and  a  study  of  the  first 
cleavage-spindle  shows  that  the  inequality  is  unmistakably 
foreshadowed  before  the  least  outward  sign  of  division  appears  ; 
for  the  asters  at  the  spindle-poles  are  conspicuously  unequal 
in  size,  the  larger  aster  corresponding  with  tho  future  larger 
cell  (Diagram  II).     This  difference  is  not  conn.cted  with  any 

determinable  Mechanical 
conditions  ;  foi  the  centro- 
somes  lie  nearl}/  equidistant 
from  the  membrane  (the 
^g<g  is  spherical),  and  the 
deutoplasm  shows  no  per- 
ceptible inequality  in  hori- 
zontal distribution.  The 
conclusion  seems  unavoid- 
able that  the  differentiation 
in  size  is  caused  by  a  specific 
form  of  activity  in  the 
cytoplasm  (or  archoplasm), 
occurring  prior  to  cell-division.  But  if  a  differentiation  in 
size  may  have  such  an  origin,  we  may  fairly  argue  that  other 
differentiations  may  likewise  precede  cell-division,  and  that 
in  such  cases  the  division  may  be,  in  a  sense,  qualitative. 

It  seems  to  me,  that  in  these  considerations  we  may  find,  in 
some  measure,  a  reconciliation  between  the  extremes  of  both 
the  rival  theories  under  discussion — that  we  may  consistently 
hold  with  Driesch  that  the  prospective  value  of  a  cell  may  be 
a  function  of  its  location,  and  at  the  same  time  hold  with  Roux 
that  the  cell  has,  in  some  measure,  an  independent  power  of 
self-determination  due  to  its  inherent  specific  structure.  Such 
a  view  is  only  possible,  however,  if  we  regard  the  specific  struc- 
ture of  the  cell  to  have  arisen  not  through  the  segregation  and 
isolation  within  its  boundaries  of  special  idioblasts  or  germ- 
substances,  that  have  been  sifted  out  by  qualitative  division, 
but  through  a  physiological  specialization  (as  de  Vries  and 
Hertwig  insist)  that  may  have  taken  place  before,  during,  or 
after  cell-division,  according  to  circumstances.     If  differentia- 


DlAGRAM    II. 


THE   MOSAIC   THEORY  OE  DEVELOPMENT.  \x 

tion  precedes  or  accompanies  division,  the  latter  process  may 
be  in  a  sense  qualitative.  If  it  follows,  division  will  be  purely 
quantitative,  and  in  such  a  case  we  may  rightly  speak  of  differ- 
entiation as  a  result  of  cellular  interaction.  The  segmentation 
of  the  Qgg  presents  more  or  less  of  a  mosaic-like  character, 
according  to  the  period  at  which  differentiation  appears,  and 
the  rate  at  which  it  proceeds,  as  expressed  in  limitations  of 
the  power  of  development  in  the  individual  blastomeres,  and 
their  differences  in  size  and  structure. 

The  general  interpretation  of  development  which  I  have  thus 
endeavored  to  sketch  will  be  found  to  differ  widely  in  some 
respects  from  that  set  forth  in  one  of  the  subsequent  lectures 
of  this  volume,  from  which,  through  Professor  Whitman's 
courtesy,  I  am  enabled  to  quote.  Whitman  argues  that 
"cell-orientation  may  enable  us  to  infer  organization,  but  to 
regard  it  as  a  measure  of  organization  is  a  serious  error." 
"The  question  as  to  the  presence  of  organization,"  he  says, 
"  is  not  settled  by  the  form  of  cleavage.  Eggs  that  admit  of 
complete  orientation  at  the  first  or  second  cleavage,  or  even 
before  cleavage  begins,  are  commonly  supposed  to  reflect 
precociously  the  later  organization,  while  eggs  in  which  such 
early  orientation  is  impossible  are  supposed  to  be  more  or  less 
completely  isotropic  and  destitute  of  organization.  When  the 
region  of  apical  growth  is  represented  by  conspicuous  telo- 
blasts,  the  fate  of  which  is  seen  to  be  definitely  fixed  from 
the  moment  of  their  appearance,  we  find  it  impossible  to  doubt 
the  evidence  of  organization,  or  '  precocious  differentiation '  as 
it  is  conventionally  called.  When  the  same  region  is  composed 
of  more  numerous  cells,  among  which  we  are  unable  to  distin- 
guish special  proliferating  cells,  we  lapse  into  the  irrational 
conviction  that  the  absence  of  definitely  orientable  cells  means 
just  so  much  less  organization." 

It  would  be  manifestly  out  of  place  to  enter  here  upon  any 
of  the  interesting  discussions  suggested  by  the  passage  just 
quoted,  and  I  will  therefore  only  add  that  Professor  Whitman's 
position  seems  to  me  to  rest  upon  a  special  and  peculiar  use 
of  the  word  "organization,"  and  that  his  view  leads  to  a  denial 
of  the  principle  of  epigenesis.     No  one  would  maintain  that 


14  BIOLOGICAL   LECTURES. 

the  living  ^gg  is  'destitute  of  organization,"  but  neither  can 
any  one  maintain  that  the  egg-organization  is  identical  with 
that  of  the  adult.  Development  is  essentially  a  transformation 
of  one  form  of  organization  into  another  along  the  path  of 
cell-division  and  cell-differentiation  ;  and  it  is  undeniable  that 
the  adult  form  of  organization  is  thus  expressed  earlier  in  some 
cases  than  in  others  —  for  example,  in  the  segregation  of  the 
germ-layers  in  the  polyclade,  as  compared  with  the  annelid  or 
gasteropod.  We  are  still  profoundly  ignorant  of  the  nature 
and  causes  of  differentiation,  and  of  its  precise  relation  to 
cell-formation  ;  and  the  question  is  probably  not  yet  ripe  for 
discussion.  It  is,  however,  impossible  to  maintain  that  differ- 
entiation in  the  Metazoa  is  entirely  independent  of  cell-forma- 
tion, when  we  recall  the  multitude  of  cases  in  which  the  lines 
of  differentiation  coincide  with  cell-boundaries. 


SECOND    LECTURE. 

THE    FERTILIZATION    OF   THE    OVUM. 

E.  G.   CONKLIN. 

In  the  history  of  the  biological  sciences  perhaps  no  problem 
has  received  more  attention  than  the  fertilization  of  the  ovum. 
The  first  important  advance  in  our  knowledge  of  this  phe- 
nomenon within  recent  years  was  made  by  O.  Hertwig^  about 
twenty  years  ago.  He  showed  that  after  a  period  of  prepara- 
tion in  which  the  Qgg  cell  extrudes  two  small  corpuscles,  the 
polar  bodies,  the  nuclei  of  the  male  and  female  cells  fuse  to 
form  the  first  or  segmentation  nucleus  of  the  new  organism. 
He  therefore  held  that  the  process  of  fertilization  consisted 
essentially  in  the  fusion  of  two  nuclei  coming  from  different 
individuals. 

This  idea  has  dominated  biology  for  the  past  decade,  and  it 
is  the  generally  accepted  view  to-day.  In  his  recent  work,  Die 
Zelle  tmd  die  Gewebe,  Hertwig  says  (p.  220),  ''The  nuclear  sub- 
stances which  are  derived  in  equal  quantities  from  two  different 
individuals,  are  the  only  essential  substances  upon  whose  union 
the  act  of  fertilization  depends  ;  they  are  the  real  fertilization 
materials.  All  other  substances,  such  as  protoplasm,  yolk, 
nuclear  sap,  etc.,  have  nothing  to  do  with  fertilization  as  such." 
It  is  well  known  that  Weismann  in  his  various  essays  and 
works  upon  heredity  has  expressed  himself  as  fully  satisfied 
that  the  essence  of  fertilization  consists  in  the  fusion  of  the 
nuclei  of  the  ovum  and  spermatozoon.  In  fact  his  whole 
theory  is  to  a  very  large  extent  founded  upon  this  fundamental 
assumption  that  fertilization  is  essentially  a  nuclear  process. 
And  quite  recently  Boveri,^  after  a  full  discussion  of  the  ques- 

1  O.  Hertwig,  Beitrage  zur  Kenntniss  der  Bildung,   Befruchtung  und  Theilung 
des  thierischen  Eies.     Morphol.  Jahrbi'icher,  1875,  1877,  1878. 

2  Boveri,  Befruchtung.     Ergebnisse  der  Anatomie  u.  Entiuick.,  1892. 


1 6  BIOLOGICAL   LECTURES. 

tion,  concludes  with  these  words  :^  "Their  union  [that  of  the 
Qgg  and  sperm  nucleus]  is  not  the  condition  but  the  goal  of 
fertilization,  and  in  this  sense  the  statement  is  true  to-day  in 
which  O.  Hertwig  summed  up  the  results  of  his  first  funda- 
mental investigations,  that  '  the  essential  thing  in  fertilization  is 
the  union  of  egg  and  spejin  nucleus!  " 

It  is  only  within  the  most  recent  times  that  a  different  view 
has  arisen,  and  for  the  sake  of  clearness  I  will  sketch  briefly 
the  rise  of  the  idea  that  fertilization  is  not  a  purely  nuclear 
phenomenon,  that  it  does  not  consist  simply  in  a  union  of 
nuclei  coming  from  different  individuals,  but  rather,  as  it  seems 
to  me,  in  a  union  of  all  the  essential  parts  of  the  reproductive 
cells,  cytoplasm  as  well  as  nuclei. 

In  1873  Hermann  Fol  ^  described  in  the  eggs  of  a  jelly-fish 
two  star-shaped  figures  or  asters  at  the  two  poles  of  the 
nucleus,  and  one  year  later  E.  Van  Beneden  ^  described  a 
polar  corpuscle  as  present  in  the  cytoplasm  during  the  karyoki- 
netic  division  of  the  nucleus  in  some  small  parasitic  organisms, 
the  Dicyemidae  ;  but  it  was  certainly  not  until  a  much  later 
date  that  anything  satisfactory  was  known  of  these  bodies. 

In  1887,  only  six  years  ago.  Van  Beneden^  in  his  work  on 
the  fertilization  of  the  ^gg  of  Ascaris,  a  thread-worm  inhabit- 
ing the  intestine  of  the  horse,  gave  a  very  minute  account 
of  two  granular  bodies,  the  spJihes  attractives  which  he 
believed  to  be  present  at  all  times  in  the  cytoplasm  of  the  cell. 
He  described -each  sphere  as  consisting  of  a  central  refractive 
body,  the  central  corpuscle,  around  which  was  a  clear  space,  the 
medullary  zone,  which  in  turn  was  surrounded  by  a  deeply 
staining  granular  area,  the  cortical  zone,  Fig.  i,  A  and  C. 
Although  he  regarded  these  spheres  as  permanent  organs  of 
the  cell,  he  did  not  know  how  they  originated  in  the  Qgg  under- 
going fertilization,  but  he  thought  that  the  two  spheres  appeared 
simultaneously  in  the  Qgg  as  newly  formed  structures,  and  he 

1  Loc.  cit.,  p.  433. 

2  Hermann   Fol,   Die  erste  Entwicklung  des  Geryonideneies.     Jenaische  Zeit- 
schrift,  1873. 

3  E.  Van  Beneden,  Recherches  sur  les  Dicyemides.     Bull.  Acad.  roy.  Belg.,  1874. 
*  Van  Beneden  et  Neyt,  Nouvelles  Recherches  sur  la  Fecondation  et  la  Division 

mitosique  chez  I'Ascaride  megalocephale. 


THE  FERTILIZATION  OF   THE    OVUM.  \J 

believed  that  they  were  derived  "■  from  the  division  of  the  Qgg 
nucleus  after  it  had  given  rise  to  the  second  polar  body"  (p.  60). 
As  described  by  Van  Beneden,  the  position  of  the  attraction 
spheres  at  their  earliest  appearance,  is  shown  in  Fig.  i  A. 
They  appear  together  in  close  proximity  to  the  female  pro- 
nucleus and  at  a  considerable  distance  from  the  male  pro- 
nucleus. Van  Beneden  therefore  supposed  that  the  male 
pronucleus  had  nothing  to  do  with  their  formation.  In  later 
stages,  Fig.  i,  B  and  C,  the  two  spheres  begin  to  separate, 
the  spindle  fibres  appearing  between  their  central  corpuscles 
and  at  the  same  time  the  two  pronuclei  approach  each  other 
and  the  first  cleavage  spindle  is  formed,  in  large  part  at  least, 
from  the  two  attraction  spheres. 

One  year  later,  1888,  Boveri  ^  described  these  bodies  in 
the  same  Qgg,  that  of  Ascaris  ;  the  central  corpuscle  of  Van 
Beneden  he  called  the  ccjitrosoine,  and  the  dark  granular  sub- 
stance surrounding  this,  which  probably  corresponds  to  the 
cortical  zone  of  Van  Beneden,  he  named  the  archoplasm.  The 
relation  of  these  parts  to  each  other,  and  to  the  pronuclei,  is 
shown  in  Fig.  i,  D,  E  and  F,  which  are  taken  from  Boveri. 
When  first  seen  in  the  ovum,  the  male  pronucleus  lies  in  the 
midst  of  a  mass  of  granular  material,  the  archoplasm.  Later 
it  moves  out  of  this,  and  in  the  place  where  it  first  lay  a  single 
highly  refractive  body,  the  centrosome,  appears.  The  centro- 
some  is  at  first  single  but  later  it  divides,  as  shown  in  E,  and 
then  around  each  of  the  centrosomes  the  archoplasm  aggregates 
to  form  two  granular  spheres.  Meanwhile  the  two  pronuclei 
enlarge  greatly  and  approach  each  other  while  the  spindle 
fibres  are  formed  from  the  two  spheres  of  archoplasm.  With 
regard  to  the  origin  of  the  constituents  of  the  archoplasmic 
system,  Boveri  believed  that  the  centrosome  was  derived  from 
the  spermatozoon,  since  it  first  appears  in  the  archoplasm  at 
the  very  place  previously  occupied  by  the  male  pronucleus, 
while  the  archoplasm  itself,  he  supposed,  came  entirely  or  at 
least  in  large  part  from  the  ^gg  cell.^ 

^  Boveri,  Zellen-Studien,  Heft  2,  Die  I]efruchtung  und  Theilung  des  Eies  von 
Ascaris  megalocephala,  1888. 
-  Loc.  cit.,  p.  167. 


1 8  BIOLOGICAL   LECTURES. 

Two  years  ago  Hermann  Fol  ^  published  a  preliminary  account 
of  the  fertilization  of  the  ^g^  of  a  sea-urchin,  in  which  he  com- 
municated the  new  and  remarkable  fact  that  each  of  the  sexual 
cells,  ovum  as  well  as  spermatozoon,  contains  a  kinetic  center 
or  centrosome,  which  he  called  respectively  the  ovocenter  and 
the  spcrmocentcr.  When  the  spermatozoon  enters  the  ovum 
the  spermocenter  precedes  the  nucleus  of  the  male  cell, 
Fig.  I  G,  and  finally  reaches  a  point  on  the  surface  of  the 
female  pronucleus  opposite  the  ovocenter  ;  then  the  male  pro- 
nucleus comes  to  lie  closely  against  the  surface  of  the  female 
pronucleus,  though  it  does  not  intimately  fuse  with  it.  The 
two  centers  then  divide.  Fig.  i  H,  and  the  half-centers  push- 
ing apart  move  in  opposite  directions  around  the  cleavage 
nucleus  until  one  half  of  the  ovocenter  meets  half  of  the 
spermocenter  at  a  point  about  90°  from  that  originally  occu- 
pied by  the  centers.  Fig.  i  I.  By  the  fusion  of  these  half- 
centres,  one  derived  from  the  ovocenter  the  other  from  the 
spermocenter,  the  astrocenters  are  formed.  Around  each  of 
these  astrocenters  there  is  formed  a  clear  space,  the  astrocoel, 
which  probably  corresponds  to  the  medullary  zone  of  Van 
Beneden,  as  the  astrocenter  corresponds  to  the  central  cor- 
puscle, while  the  astrocoel  is  surrounded  by  a  zone  of  astral 
radiaiionSj  which  is  probably  the  cortical  zone  of  Van  Beneden 
and  the  archoplasm  of  Boveri.  From  these  facts  regarding 
the  formation  of  the  astrocenters,  Fol  concluded  that  ''fertiliza- 
tion consists  not  only  in  the  adding  together  of  two  pronuclei 
derived  from  individuals  of  different  sexes,  but  also  in  the 
fusion  of  four  half-centers  derived  from  the  father  and  the 
mother  into  two  new  bodies,  the  astrocenters."  ^ 

In  November  of  the  same  year,  1891,  Guignard^  published 
a  most  admirable  account  of  the  process  of  fertilization  in  some 
of  the  flowering  plants.  He  showed  that  the  male  pronucleus, 
which  is  brought  into  close  proximity  to  the  female  pronucleus 
by  the  growth  of  the  pollen  tube,  is  always  preceded  by  two 

1  Hermann  Fol,  Die  Centrenquadrille  eine  neue  Episode  aus  der  Befruchtungs- 
geschichte.     Anat.  Anzeiger,  May,  1891. 

2  Loc.  cit.,  p.  274. 

3  Guignard,  Nouvelles  Etudes  sur  la  Fecondation.  Anuales  des  sciences  natter. 
Tom.  14,  Botanique,  1891. 


THE   FERTILIZATION  OF    THE    OVUM. 


19 


Fig.  1.  —  Diagrams  showing  the  process  of  fertilization  according  to  different 
authors.  The  first  row  (A,  B  and  C),  for  Ascaris,  according  to  Van  Beneden  ; 
the  second  row,  the  same  form,  according  to  Boveri ;  the  third  row  for  an  Echinid, 
according  to  Fol  ;  the  fourth  for  Lilium,  according  to  Guignard. 


20  BIOLOGICAL   LECTURES. 

bodies,  the  spJibres  directrices,  which  are  the  equivalents  of 
Van  Beneden's  spheres  attractives  and  Fol's  asters  ;  two  of 
these  spheres  are  also  found  in  .  contact  with  the  female  pro- 
nucleus, Fig.  I  K.  The  two  spheres  which  precede  the  male 
pronucleus  join  those  which  surmount  the  female  pronucleus 
in  such  a  way  as  to  form  two  couples,  each  of  which  is  com- 
posed of  one  element  derived  from  the  male  cell,  the  other 
from  the  female  cell.  When  the  pronuclei  come  in  contact, 
the  two  couples  diverge  until  they  come  to  lie  at  opposite  poles 
of  the  nuclei.  Fig.  i  L.  Then  the  elements  of  each  couple 
fuse  together  into  a  single  sphere  with  a  single  central  cor- 
puscle, Fig.  I  M,  and  from  these  spheres  the  first  cleavage 
spindle  is  formed.  Guignard  concludes,  therefore,  that  fertili- 
zation is  not  a  purely  nuclear  phenomenon.  "■  It  consists  not 
only  in  the  union  of  two  nuclei  of  different  sexual  origin,  but 
also  in  the  fusion  of  two  protoplasmic  bodies  whose  essential 
elements  are  the  sphtres  directrices  of  the  male  cell  and  of  the 
female  cell.  Even  if  the  nuclei  are  of  great  importance  in  the 
transmission  of  hereditary  properties,  the  permanent  presence 
of  spheres  directrices  in  the  sexual  and  somatic  cells,  and  above 
all  their  fusion  at  the  moment  of  fecundation,  oblige  us  to 
assign  to  the  protoplasm  the  primordial  role  in  the  accom- 
plishment of  this  phenomenon.  This  fusion  appertains  to 
the  very  essence  of  fertilization  ;  it  is  necessary  for  the 
formation  and  subsequent  evolution  of  the  Qgg''  ^ 

More  than  a  year  ago  (July,  1892),  I  found  that  the  eggs  of 
one  of  our  marine  Gasteropods,  Crepidiila  plana,  offered  excep- 
tional advantages  for  the  study  of  the  phenomena  of  fertiliza- 
tion. In  this  ^gg,  and  that  of  other  species  of  the  same  genus, 
I  had  been  able  to  trace  the  cell-lineage  to  more  than  one  hun- 
dred cells,  and  last  summer,  with  more  favorable  material  and 
better  methods,  I  was  able  to  follow  in  surface  preparations,  as 
well  as  in  sections,  the  movements  of  the  male  and  female  pro- 
nuclei, and  what  is  much  more  important,  the  whole  history  of 
the  asters  ^  from  the  time  the  first  polar  body  is  formed  and  the 

1  Loc.  cit.,  p.  276. 

2  For  these  permanent  organs  of  the  cell,  known  by  various  authors  as  the 
'■^ spheres  attractives^^''  '^ spheres  directrices,'"  " archoplasmic  bodies,"  "periplasts," 


THE   FERTILIZATION   OF   THE    OVUM. 


21 


spermatozoon  enters  the  ^gg  until  a  late  stage  in  the  cleavage 
of  the  fertilized  ovum.  In  the  main,  my  observations  on  the 
fertilization  confirm  those  of  Fol,  concerning  which  a  good 
deal  of  doubt  has  been  expressed  by  some  authorities,  though 
in  some  respects  they  differ  from  these  and  resemble  more 
closely  the  results  obtained  by  Guignard. 

Since  the  aster  plays  so  important  a  part  in  the  process  of 
fertilization,  it  will  be  well  to  begin  with  a  description  of  this 
structure.  Every  aster  undergoes  periodical  changes  in  form 
and  size  as  well  as  constitution.  When  it  has  reached  its 
largest  size,  which  is  just  before  it  divides,  it  is  a  spherical  or 
ellipsoidal  body,  almost  as  large  as  the  nucleus.  Fig.  2.  It 
has    a    very  definite   out- 


line from  which  radiating 
rows  of  granules  or  micro- 
somes ca,n  be  traced  to  all 
parts  of  the  cell.  The 
sphere  itself  consists  of 
an  outer,  darkly  granular 
zone  and  of  a  central  clear 
area.  The  granules  of 
the  outer  zone  can  in  no 
way  be  distinguished  from 
the  microsomes  scattered        „  ^,     .        ,  r  .     .      ^ 

t  IG.  2.  —  Section  of  one  of  the  first  four 
throughout  the  cell  ;  their  micromeres  of  C.  plana  showing  the  structure 
general  appearance  is  very      o^  the  aster  and  its  relations  to  other  parts  of 

similar  and  they  stain  in     ^^^  ^^"• 

the  same  way.  Moreover,  at  certain  stages  in  the  history 
of  the  aster  it  loses  its  definite  outline,  astral  radiations 
proceed  from  it  in  every  direction,  and  the  granules  of 
which  it  is   composed   become   confluent  with  the  microsomes 

"para-nuclei,"  etc.,  I  have  decided  to  employ  the  name  "aster,"  first  used  by 
Fol,  I  believe.  This  name  has  the  advantage  of  brevity,  simplicity  and  accuracy, 
which  cannot  be  said  of  the  others.  Some  of  these  names  are  not  only  unwieldy, 
but  absolutely  misleading.  For  example,  the  spheres  attractives  have  the  function 
of  repulsion  as  well  as  attraction  ;  the  spheres  directrices  do  not,  in  all  cases  at  least, 
direct  the  nuclear  division,  and  the  same  may  be  said  of  the  archoplasm  or  "con- 
trolling" plasm.  The  exact  connotation  of  the  words  "periplast"  and  "para- 
nucleus" is  so  doubtful  that  they  cannot  safely  be  used. 


22  BIOLOGICAL   LECTURES. 

of  the  cell ;  at  the  same  time  the  central  clear  area  disappears. 
This  occurs  in  the  formation  of  every  nuclear  spindle  ;  in  the 
later  stages  of  the  nuclear  division,  when  the  central  portion 
of  the  spindle  begins  to  disappear,  the  granules  which  were 
distributed  along  the  radiating  fibres  are  gathered  together 
in  such  a  way  that  one  or  more  rows  of  them  are  pressed 
closely  together  to  form  the  definite  boundary  of  the  aster, 
while  within  this  boundary  the  granules  are  less  compactly 
arranged.  This  graiiidar  zone,  with  its  radiations,  corres- 
ponds, I  believe,  to  the  cortical  zone  of  Van  Beneden  and 
the  archoplasm  of  Boveri. 

The  central  clear  area  probably  corresponds  to  the  medullary 
zone  of  Van  Beneden  and  the  astrocoel  of  Fol,  and  in  speaking 
of  it  hereafter  I  shall  employ  the  latter  name.  The  astrocoel 
always  contains  a  large  number  of  irregularly  scattered  granules, 
which  are  considerably  larger  than  those  of  the  outer  zone  but 
are  not  peculiar  in  any  other  respect.  They  show  the  same 
micro-chemical  reactions  as  the  microsomes,  and  at  an  early 
stage  in  the  history  of  each  aster  they  are  closely  connected 
with  the  granules  of  the  outer  zone.  After  the  nuclear  spindle 
has  been  formed  these  granules  disappear,  and  in  their 
place  is  found,  at  each  pole  of  the  spindle,  a  darkly  staining 
body  much  larger  than  any  one  of  the  central  granules. 
This  is  doubtless  the  central  corpuscle  of  Van  Beneden  or 
centrosome  of  Boveri,  and  I  cannot  doubt  that  the  numerous 
central  granules  represent  a  fragmented  or  scattered  centiv- 
some. 

The  structure  of  the  outer  granular  zone  of  the  aster,  its 
micro-chemical  reactions,  and  particularly  its  method  of  growth, 
seem  to  me  to  indicate  plainly  that  this  portion  of  the  aster 
is  merely  a  part  of  the  general  cytoplasm  temporarily  modified 
or  differentiated  for  a  particular  function.  Regarding  the 
astrocoel  and  centrosomes  there  is  more  doubt,  but  I  believe 
that  the  evidence  is  clearly  in  favor  of  the  view  recently 
expressed  by  Watase,^  that  these  structures  are  also  a  part 
of  the  cytoplasm.  Whatever  the  ultimate  origin  of  the 
centrosomes  may  be,  there  is  no  doubt  that  in  Crepidula  they" 

1  Watase,  Homology  of  the  Centrosome.    Jotu\  Morph.,  Vol.  8,  No.  2. 


THE   FERTILIZATION  OF    THE    OVUM. 


23 


do  not  go  back  into  the  nucleus  after  every  division,  as 
Brauer^  asserts  is  the  case  in  Ascaris.  It  therefore  seems 
highly  probable  that  the  entire  aster  is  a  cytoplasmic  struc- 
ture, temporarily  modified  or  differentiated  for  the  purpose 
of  contraction  and  expansion,  whose  chief  function  in  the 
reproductive  cells  is  to  bring  the  pro-nuclei  together,  accom- 
plish nuclear  division,  and  move  the  nuclei  from  place  to  place 
in  the  resulting  cells. 

To  return  to  the  process  of  fertilization  :  the  spermatozoon 
usually,  though  not  invariably,  enters  the  ovum  near  the  vege- 
tal pole.  I  have  not  observed  it  in  the  actual  process  of  enter- 
ing, though  I  have  seen  it  immediately  afterward.  In  such 
cases  it  consists  of  a  small  conical  or  sometimes  fusiform 
nucleus,  surrounded  by  a  clear  non-granular  area.  Fig.  3.  At 
this  stage  the  sperm  nucleus 
consists  entirely  of  chromatin 
closely  packed  together;  there 
is  no  nuclear  sap  and  no  aster 
is  visible,  though,  perhaps,  the 
clear  area  surrounding  the 
nucleus  may  be  taken  as  an 
indication  of  the  presence  of 
such  a  body.  In  Fig.  3  the 
Q^^  nucleus  is  shown  in  the 
process  of  division  preparatory 
to  the  formation  of  the  first 
polar  body.  There  are  two 
centrosomes  at  the  upper  pole 
of  the  spindle,  though  but  one  is  to  be  seen  at  the  lower  pole. 
The  centrosome  at  the  upper  pole  has  divided  thus  early, 
preparatory  to  the  division  of  the  chromatin  of  the  first 
polar  body.  This  division  occurs  soon  after  the  polar  body 
is  formed.  The  surface  of  the  ^gg  is  indented  over  the 
upper  pole  of  the  spindle,  thus  indicating,  as  it  seems  to  me, 
that  the  astral  fibres  are  here  attached  to  the  surface  and  are 
drawing  it  in  by  their  contraction. 

1  Brauer,    Zur  Kenntniss  der   llerkunft    des   Centrosomes.      Biol.  Ccntralblatt, 
13d.  13,  Nos.  9  and  to. 


Fig.  3.  —  C.  plana  ;  formation  of  the 
first  polar  body  ;  at  the  left  the  sperma- 
tozoon has  just  entered  the  ovum. 


24 


BIOLOGICAL   LECTURES. 


The  spermatozoon  usually  enters  the  ovum  at  about  the  same 
time  that  the  first  polar  body  is  being  formed,  though  in  a  con- 
siderable number  of  eggs  it  does  not  enter  until  after  both 
polar  bodies  have  been  extruded.  Soon  after  its  entrance,  the 
sperm  nucleus  begins  to  move  toward  the  ^g'g  nucleus.  This 
motion  is  quite  slow,  several  hours  (four  to  eight)  being  neces- 
sary to  bring  the  two  nuclei  together  ;  it  is,  therefore,  possible 
to  find  almost  every  stage  in  this  process  in  eggs  which  have 
been  fixed  and  stained.  During  the  whole  of  this  journey 
toward  the  ^gg  nucleus,  the  sperm  nucleus  continually  increases 
in  size  ;  but  before  this  nucleus  shows  any  appreciable  enlarge- 
ment, and  when  it  is  removed  from  the  Qg<g  nucleus  by  almost 
the  whole  diameter  of  the  ovum,  the  sperm  aster  appears  as  a 
granular  sphere,  considerably  larger  than  the  sperm  nucleus, 
and  lying  immediately  in  advance  of  it,  Fig.  4.  Throughout 
the  approach  of  the  two  pronuclei,  the  sperm  aster  precedes 
the  sperm  nucleus,  and,  as  I  believe,  actually  leads  it  to  the 
^g'g  nucleus. 

As  already  explained,  Boveri  believes  that  the  centrosome 
of  the  new  organism  is  derived  exclusively  from  the  sperma- 
tozoon. In  his  latest  work  (already  referred  to)  he  says  that, 
in  the  case  of  Ascaris,  there  is  neither  centrosome  nor  aster 
present  in  the  formation  of  the  two  polar  bodies,  although 
they  were  present  at  an  earlier  stage  in  the  oogenesis  ;  he 
therefore  concludes  that  in  this  case  the  centrosomes  of  the 
segmentation  spindle,  which  forms  later,  must  be  derived 
exclusively  from  the  sperm  centrosome.  Vejdovsky^  has 
reached  the  same  conclusion  with  regard  to  one  of  the  anne- 
lids, Rhinchelmis.  He  says,  regarding  Fol's  communication 
relative  to  the  ovocenter,  that  no  one  has  hitherto  seen  such 
a  body  in  connection  with  the  female  pronucleus,  and  that  he 
conceives  it  to  be  the  scarcely  functional  remnant  of  the 
Eikei'nperiplaste,  or  ^gg  aster.  *'  It  is  therefore,"  he  says, 
'*  questionable  to  assume  the  presence  of  an  ovocenter  in 
order  to  make  a  general  law  that  in  fertilization  not  only  the 
pronuclei,  but  also  the  halves  of  the   ovocenter  and   spermo- 

^  Vejdovsky.  Bemerkungen  zur  Mitteilung  H.  Fol's  "Contribution  a  I'histoire 
de  la  fecondation."     Anat.  Anzeiger,  Bd.  6,  No.  13. 


THE  FERTILIZATION  OF   THE   OVUM.  25 

center  unite.     The  facts  observed  in  the  case  of  Rhinchelmis 
speak  against  Fol's  theory." 

In  the  face  of  the  conclusions  of  these  well-known  investi- 
gators, it  is  interesting  to  find,  in  the  case  of  the  Crepidula 
^g^,  a  well  marked  centrosome  and  surrounding  parts  of  the 
aster  present  at  each  pole  of  the  spindle  in  the  formation  of 
each  of  the  polar  bodies  ;  and  immediately  after  the  second 
polar  body  has  been  extruded,  and  while  the  sperm  nucleus 
and  aster  are  still  far  removed  from  the  ^g<g  nucleus,  a  large 
and  distinct  aster  can  be  seen  in  contact  with  this  nucleus. 
This  Qgg  aster  lies  below  the  ^gg  nucleus,  and  usually  slightly 
to  one  side  of  the  chief  axis  of  the  ovum,  as  shown  in  Fig.  4. 


Fig.  4.  —  Ovum  of  C. plana,  side  view;  FiG.  5. —  Ovum  of  C.  plana  seen  from 
the  asters  are  shown  in  dotted  outline,  upper  pole ;  in  this  and  the  following 
the  clear  spheres  with  dark  centers,  at  figures  the  male  aster  and  nucleus  lie  to 
the  upper  pole,  are  the  two  polar  bodies,    the  left,  the  female  to  the  right.     First 

contact  of  the  two  asters. 

It  is  at  first  much  larger  than  the  sperm  aster,  and  in  fact 
remains  larger  until  it  enters  upon  ^'ia  MaixJie  dc  la  Quadrille T 
The  sperm  nucleus  always  approaches  the  ^gg  nucleus  from 
below  and  in  such  a  way  that  the  sperm  aster  is  directed 
toward  the  egg  aster.  Fig.  4.  The  force  which  draws  the  two 
pronuclei  together  seems  to  exist  between  the  two  asters  rather 
than  between  the  pronuclei.  Accordingly,  in  the  progress  of 
the  sperm  nucleus  toward  the  ^gg  nucleus,  the  asters  first 
come  in  contact,  Fig.  5.  In  all  movements  of  the  nucleus,  the 
latter  appears  to  be  passive  while  the  asters  are  active.     This 


26  BIOLOGICAL   LECTURES. 

principle  is  illustrated  throughout  the  whole  history  of  the 
cleavage  ;  whenever  the  nucleus  is  moved  from  one  position  to 
another  in  the  cell  it  is  preceded  by  its  aster.  The  method  by 
which  the  asters  draw  the  two  pronuclei  together  is,  I  believe, 
by  the  formation,  attachment  and  contraction  of  the  astral  or 
archoplasmic  fibrils.  In  this  connection  it  is  interesting  to 
contrast  the  methods  by  which  the  male  and  female  cells 
approach  each  other  before  and  after  the  spermatozoon  has 
reached  the  ovum.  In  the  case  of  Crepidula,  as  in  most 
other  forms,  the  spermatozoon  moves  toward  the  ovum  by  the 
lashing  from  side  to  side  of  a  long  thread-like  flagellum.  As 
soon,  however,  as  the  sperm  enters  the  ovum  this  flagellum  is 


Fig.   6.  —  Ovum    of    C.  plana  from  Fig.    7.  —  Separation    of   the    two 

upper   pole  ;    first   contact  of   the   two     asters;  the  polar  bodies  lie  immediately 
pronuclei.  over  the  female  pronucleus. 

lost  in  most  cases,  and  the  rest  of  the  progress  toward  the  Q%g 
nucleus  and  aster  must  be  accomplished  in  some  other  way. 
This,  as  just  said,  seems  to  be  done  by  the  formation  and  con- 
traction of  astral  fibers.  This  movement  of  the  sperm  cell 
within  the  ovum  is  the  result  of  protoplasmic  contractility 
no  less  than  is  the  movement  of  the  spermatozoon  outside  of 
of  the  nucleus,  operating,  however,  in  a  slightly  different  way. 
After  the  two  asters  have  come  in  contact,  they  move  slightly 
to  one  side,  remaining  however  connected,  though  individually 
distinct,  and  the  two  pronuclei  then  come  together,  Fig.  6. 
Even  at  this  time,  the  sperm  aster  and  nucleus  are  usually  a 


THE   FERTILIZATION  OF   THE    OVUM.  27 

little  smaller  than  those  of  the  ^gg  cell,  and  they  frequently 
remain  slightly  smaller  as  long  as  they  can  be  distinguished. 
In  cases  where  there  is  no  appreciable  difference  in  size 
between  the  two  pronuclei,  the  one  may  be  distinguished  from 
the  other,  as  long  as  they  remain  distinct,  by  the  position  of 
the  polar  bodies  which  lie  directly  over  the  female  pronucleus. 
After  the  two  pronuclei  have  met,  the  two  asters  begin  to 
move  apart.  They  continue  to  separate,  moving  around  the 
appressed  nuclei,  until  they  lie  at  opposite  poles.  Fig.  7.  The 
sperm  aster  now  lies  on  the  outer  side  of  the  sperm  nucleus, 
and  the  ^gg  aster  on  the  outer  side  of  the  ^gg  nucleus  ;  it  is 
thus  seen  that  the  position  which  the  asters  occupy  relative  to 


Fig.  8.  —  The  halves  of  the  male  and  Fig.  9.  —  The  halves  of  the  female 
female  asters  about  to  unite  at  the  aster  at  the  poles  of  the  pronuclei ;  the 
poles  of  the  pronuclei.  male  aster  still  undivided. 

the  pronuclei,  is  just  the  reverse  of  that  which  obtained  previ- 
ous to  the  meeting  of  the  two  pronuclei.  It  must  also  be 
allowed,  I  think,  that  the  function  now  exercised  by  the  asters 
must  be  the  reverse  of  that  which  prevailed  before  the  pro- 
nuclei met.  Then,  by  active  contraction,  they  drew  the  two 
pronuclei  together;  now,  by  active  expansion,  they  diverge,  move 
to  opposite  poles,  and  press  the  pronuclei  together.  This  func- 
tional alternation  of  contraction  and  expansion,  or  perhaps 
better,  attraction  and  repulsion,  is  manifest  not  only  during 
fertilization,  but  throughout  the  entire  process  of  cleavage. 
The  contraction  can  be  seen  in  the  way  in  which  the  asters 


28 


BIOLOGICAL   LECTURES. 


draw  the  nuclei  from  one  place  to  another  in  the  cell,  as  well 
as  in  the  pulling  asunder  of  the  chromatic  elements  of  the 
nucleus,  the  expansion  in  the  division  of  the  asters  and  the 
subsequent  divergence  of  the  resulting  daughter  asters,  as  well 
as  in  the  formation  of  the  karyokinetic  spindle  and  the  pushing 
together  of  the  chromatic  elements  into  the  equatorial  plate. 

After  the  asters  have  reached  the  outer  sides  of  the  two  pro- 
nuclei, each  divides  into  two  half-asters,  which  diverge  from 
each  other  until  they  come  to  lie  at  opposite  poles  of  the 
nuclei  and  in  the  plane  of  contact  between  the  two.  At  this 
stage,  therefore,  there  is  found  at  each  pole  of  the  two  pro- 
nuclei one-half  of  the  sperm  aster  and  one-half  of  the  ^gg  aster, 
Fig.  8.  Each  of  these  couples  soon  fuses  into  a  single  aster, 
and  the  two  asters  thus  formed  lie  at  opposite  poles  of  the 
first  cleavage-spindle-,  Fig.  lo,  and  from  them  all  the  other 
asters  of  the  developing  ovum  are  derived. 

As  an  interesting  variation  of  this  more  usual  behavior  of 
the  asters,  it  should  be  mentioned  that  in  cases  where  the 
sperm  nucleus  and  aster  meet  the  corresponding  parts  of  the 

^gg  cell,  while  there  is  yet 
considerable  disparity  in  size 
between  the  two,  the  ^gg 
aster  after  having  reached  its 
full  size  divides,  and  the  two 
half-asters  pass  to  the  two 
poles  of  the  nuclei,  while  the 
sperm  aster,  during  all  this 
time,  remains  undivided  until 
it  has  reached  its  full  size, 
when  it  divides,  and  its  halves 
move  around  to  meet  the 
waiting  halves  of  the  ^g'g 
aster,  Fig.  9. 

With  the  fusion  of  the  half- 
asters,  one  part  of  the  fecunda- 
tion, and  that  a  very  important  one,  is  completed,  although  the 
two  pronuclei  may  still  be  recognized  as  such.  In  fact,  the 
boundary  line  between  the  ^gg  and  the  sperm  nucleus  can  be 


Fig.  10.  —  Formation  of  the  first 
cleavage-spindle.  The  half-asters  have 
fused,  but  a  trace  of  the  nuclear  mem- 
brane remains  between  the  two  pro- 
nuclei. 


THE   FERTILIZATION  OF   THE    OVUM.  29 

distinguished  even  after  the  first  cleavage  spindle  begins  to 
form,  and  their  chromatin  masses  remain  distinct,  Fig.  10, 
until  the  equatorial  plate  stage. 

After  the  chromatin  of  the  two  pronuclei  has  assumed  the 
shape  of  distinct  rods,  the  chromosomes,  and  before  these  rods 
have  been  pressed  together  into  the  equatorial  plate,  it  is 
possible  to  determine  that  each  pronucleus  contains  twelve  of 
these  elements.  Since  these  elements  are  doubled  at  every 
division  of  the  .nucleus,  it  follows  that  each  of  the  first  two 
nuclei  contains  twenty-four  chromosomes,  twelve  derived  from 
the  sperm  nucleus  and  twelve  from  the  ^^^  nucleus,  and  this 
number  is  probably  constant  for  all  the  nuclei  of  this  species. 

It  is  difficult  to  define  exactly  the  time  at  which  the  two 
pronuclei  have  sufficiently  united  to  be  considered  a  single 
element,  but  perhaps  this  can  be  most  conveniently  located  at 
the  time  when  the  boundary  wall  between  the  two  vesicular 
nuclei  disappears,  although,  as  just  said,  the  two  masses  of 
chromatin  remain  distinct  until  a  somewhat  later  period.  Cer- 
tain it  is  that  a  fusion  of  the  pronuclei  to  form  a  resting  seg- 
maitation  micletis,  as  described  by  Hertwig,  does  not  take 
place. 

With  the  union  of  the  pronuclei,  the  entire  process  of 
fecundation  may  be  considered  as  ended.  So  far  from  being 
a  purely  nuclear  phenomenon,  it  must  be  evident  to  any  one 
who  follows  the  history  of  the  asters  that  they  take  an 
extremely  important  part  in  this  process.  If  we  are  amazed 
at  the  precision  with  which  the  chromatic  elements  of  the 
nucleus  are  divided  and  distributed,  we  can  be  no  less  astonished 
at  the  wonderful  directive  influence  exercised  by  the  asters 
upon  the  nuclei ;  and  if  it  is  justifiable  to  conclude  that  the 
chromosomes  have  an  extremely  important  function  in  the 
building  of  the  new  organism  because  of  the  way  in  which 
they  are  distributed,  how  is  it  possible  to  avoid  the  same  con- 
clusion with  regard  to  the  asters,  which,  as  we  have  seen,  are 
equally  divided  in  a  manner  not  clearly  understood  into  half- 
asters,  which  then  fuse  in  such  a  way  that  one-half  of  each 
aster  of  the  new  organism  comes  from  the  paternal  and  one- 
half  from  the  maternal  organism } 


30  BIOLOGICAL   LECTURES. 

Hertwig,  Boveri  and  Weismann,  as  well  as  a  number  of  other 
well-known  investigators,  assert  that  the  hereditary  substance, 
by  means  of  which  heritable  qualities  are  transmitted  from  one 
generation  to  another,  is  contained  wholly  within  the  nucleus, 
and,  speaking  more  strictly  still,  within  that  part  of  the  nucleus 
called  the  chromatin.  Since,  however,  many  of  the  characters 
of  the  cytoplasm  are  heritable,  and  in  fact  are  generally  the 
only  characters  which  are  known  by  observation  to  be  herit- 
able, these  authorities  are  compelled  to  assume  that  the  control 
of  the  cell,  if  not  the  actual  genesis  of  all  its  constituents,  is 
located  wholly  within  the  chromatin.  As  a  matter  of  fact,  it 
must  be  acknowledged  that  this  assumption  that  the  chromatin 
makes  the  cell-body  just  what  it  is  in  point  of  structure,  func- 
tion, shape,  position  and  size,  does  not  rest  upon  observation 
but  upon  supposed  theoretical  necessities.  All  these  necessi- 
ties find  their  source  in  the  assumption  that  the  nucleus,  and 
especially  the  chromatin,  is  the  only  bearer  of  heredity,  an 
assumption  which  was  wholly  justified  so  long  as  it  was  sup- 
posed that  fertilization  consisted  merely  in  the  fusion  of  the 
two  pronuclei  ;  but  now  since  it  is  known  that  the  cytoplasm, 
and  especially  the  male  and  female  asters,  take  a  very  import- 
ant part  in  the  process  of  fertilization,  it  seems  to  me  that 
such  an  assumption  is  wholly  unwarrantable. 

The  spermatozoon  does  not  cease  to  be  a  cell  the  moment  it 
has  entered  the  ovum.  Both  its  cytoplasm  (in  the  form  of  an 
aster)  and  its  nucleus  are  represented,  and  they  grow  just  as  a 
cleavage  or  tissue  cell  does  by  the  assimilation  of  food  material, 
which  in  this  case  is  contained  within  the  o^gg  cell.  Although 
within  the  ovum  the  spermatozoon  must  be  considered  a  dis- 
tinct cell,  preserving  all  its  fundamental  peculiarities,  until  that 
time  when  its  various  constituents  lose  their  identity  by  fusion 
with  corresponding  parts  of  the  ^gg  cell.  While  it  is  known 
in  several  cases  that  the  spermatozoon  introduces  a  nucleus 
and  an  aster,  which  then  fuse  with  similar  parts  of  the  ovum, 
it  is  not  known,  with  one  or  two  exceptions,  that  any  portion 
of  the  general  cytoplasm  of  the  male  cell  is  carried  into  the 
ovum.  In  the  case  of  Ascaris,  both  Van  Beneden  and  Boveri 
agree  that  a  certain  part  of  the  cytoplasm  of  the  spermatozoon 


THE   FERTILIZATION  OF   THE    OVUM. 


31 


is  carried  into  the  ^ggy  and  is  there  absorbed,  used  as  food,  by 
the  cytoplasm  of  the  ovum.  On  the  ground  of  direct  observa- 
tion, the  fusion  of  the  general  cytoplasm  of  the  sperm  with 
that  of  the  ovum  can  neither  be  affirmed  nor  denied  in  most 
cases  ;  but  it  is  a  matter  of  observation  that  there  is  a  union 
of  those  portions  of  the  cytoplasm  which  can  be  followed,  viz., 
the  asters,  and  in  view  of  what  we  know  of  conjugation  among 
the  simplest  animals  and  plants,  where  there  is  a  fusion  of 
the  cell-bodies  as  well  as  of  the  nuclei,  I  question  whether 
the  cytoplasm  which  the  sperm  carries  into  the  ovum,  in  the 
case  of  Ascaris,  merely  degenerates  and  serves  as  food  for  the 
^gg  cytoplasm.  It  seems  to  me  more  probable  that  this  sperm 
cytoplasm  does  not  act  as  so  much  dead  matter,  but  that  it  also 
takes  part  in  this  union  of  the  essential  constituents  of  the  two 
cells. 

On  a  priori  ground,  I  think  we  ought  to  expect  that  in  fer- 
tilization all  the  essential  parts  of  one  cell  would  unite  with 
corresponding  parts  of  another  cell.  In  fact,  the  form  of 
fertilization  characteristic  of  the  higher  animals  and  plants 
is  generally  supposed  to  have  been  derived  from  a  condition 
similar  to  that  which  at  present  obtains  among  the  lower 
animals  and  plants  in  which  there  is  a  fusion  of  two  entire 
cells.  Most  persons  would  probably  agree  that  fertilization 
consists  in  the  union  of  the  essential  parts  of  two  cells  ;  the 
question  is,  ''What  are  essential  parts  .^ "  It  is  known  that  if 
some  of  the  Infusoria  are  cut  to  pieces  so  that  some  of  the 
pieces  contain  portions  of  the  nucleus,  while  others  do  not,  the 
nucleated  portions  will  regenerate  all  the  lost  parts,  while  those 
pieces  which  contain  no  part  of  the  nucleus  do  not  regenerate 
but  sooner  or  later  perish.  It  is,  therefore,  certain  that  the 
cytoplasm  cannot  perform  the  normal  funtions  of  growth  and 
regeneration  apart  from  the  nucleus.  It  seems  equally  certain, 
although  much  more  difficult  of  demonstration,  that  the  nucleus 
cannot  perform  all  its  normal  functions  apart  from  the  cyto- 
plasm. Both  nucleus  and  cytoplasm  are  essential  constituents 
of  the  cell,  and  one  cannot  be  said  to  be  more  important  than 
the  other.  In  spite  of  the  assumption  of  smaller  structural 
units  within  the  cell  (such  as  the  biophors  of  Weismann,  the 


32  BIOLOGICAL   LECTURES. 

pangenes  of  De  Vries,  the  plasomcs  of  Wiesner,  which  assump- 
tion, in  one  form  or  another,  seems  to  me  a  necessity),  the 
independent  unit  of  structure  is  still  the  entire  cell,  not  cyto- 
plasm alone,  nor  nucleus  alone,  but  the  two  together.  So  far 
as  we  know,  the  cytoplasm  of  every  cell  comes  from  the  cyto- 
plasm of  some  parental  cell,  just  as  certainly  as  the  nucleus 
comes  from  a  preceding  nucleus.  Until,  therefore,  it  can  be 
shown  that  the  nucleus  can  exist  independently  of  the  cyto- 
plasm, it  is  unsound  to  assert  that  the  cytoplasm  is  not  an 
essential  constituent  of  the  cell.  And  until  some  one  has 
shown  that  cytoplasm  is  not  derived  from  pre-existing  cyto- 
plasm, but  is  the  product  of  the  nucleus,^  it  is  too  soon 
to  assert  that  the  control  of  the  entire  cell  lies  in  the 
nucleus,  and  hence  that  the  nucleus  is  the  sole  bearer  of 
heredity. 

In  seeking  to  show  that  the  nucleus  is  not  the  sole  bearer 
of  heredity,  we  are  not  confined  entirely  to  the  a  priori  argu- 
ment ;  aside  from  the  important  evidence  already  adduced  in 
the  presence  and  function  of  the  asters  observations  are  not 
altogether  wanting  to  show  that  the  cytoplasm,  in  many 
respects  at  least,  is  not  controlled  by  the  nucleus.  In  the 
early  cleavage  stages  of  Crepidula  pla^ia,  it  can  be  shown  beyond 
question  that  the  direction  of  the  cleavage,  the  size  of  the  cells 
formed,  and  the  shape  of  those  cells  is  the  result  of  cytoplasmic 
activity  rather  than  of  nuclear.^     It  is  generally  believed  that 

1  This  is,  I  know,  what  Weismann  asserts  (The  Germ  Plasm,  p.  50),  and  he 
urges  in  proof  the  observations  of  Riickert  on  the  alteration  in  size  of  the 
chromosomes  of  the  nucleus  during  the  growth  of  the  ovum  ot  the  dogfish. 
These  chromosomes  first  enlarge  greatly,  and  afterward  diminish  in  size  until 
they  are  not  much  larger  than  at  first.  Riickert,  therefore,  believes  that  the 
chromosomes  give  off  a  large  amount  of  substance  to  the  cytoplasm,  and  this 
conclusion  is  probably  correct.  It  does  not  follow,  however,  that  this  material 
controls  the  cytoplasm,  as  Weismann  assumes,  any  more  than  the  fact  that  the 
cytoplasm  supplies  the  nucleus  with  a  large  amount  of  nuclear  sap  in  its  pre- 
division  stages,  argues  that  the  cytoplasm  controls  the  nucleus.  It  is  probable 
that  each  supplies  substances  to  the  other,  and  it  is  interesting  to  note  that  at 
the  very  stage  described  by  Riickert  (the  pre-division  stage),  in  which  the  chro- 
mosomes are  giving  off  substances  to  the  cytoplasm,  the  nucleus,  in  many 
forms  at  least,  is  receiving  a  large  amount  of  material  in  the  form  of  nuclear 
sap  from  the  cytoplasm. 

2  Since  this  lecture  was  given,  I  have  found  that  Boveri,  in  his  recent  work  on 


THE   FERTILIZATION  OF   THE    OVUM.  33 

the  nuclear  spindle  predetermines  the  direction  of  the  cleavage, 
yet,  in  this  case,  the  spindle  may  be  formed  in  any  possible 
direction,  and  yet  the  cleavage  invariably  takes  place  in  the 
same  direction.  It  is  frequently  asserted  that  the  division-wall 
between  the  daughter-cells  appears  at  right  angles  to  the 
spindle,  and  yet,  in  this  case,  it  may  form  at  a  greater  or  a 
smaller  angle  than  90°.  The  direction  of  the  cleavage  is  pre- 
determined not  only  before  the  nucleus  divides,  but  long  before 
the  asters  divide.  Certain  oscillatory  movements  of  the  cyto- 
plasm, which  begin  with  the  first  division  of  the  ovum  and  can 
be  observed  throughout  a  large  part  of  the  cleavage,  determine 
with  absolute  certainty  the  direction  of  the  cleavage  before  any 
indication  of  division  can  be  found  within  the  cell.  Since. the 
direction  of  the  cleavage  is  not  determined  by  the  nucleus,  it 
follows  that  the  rotation  of  the  cells  and  the  position  which 
they  take,  with  reference  to  each  other,  are  not  determined  by 
the  nucleus  ;  and  since  it  can  be  shown  that  the  shape  of  the 
cleavage  cells  is  very  largely  the  result  of  intercellular  rela- 
tions, it  follows  that  in  this  case,  at  least,  the  shape  of  the 
cell  is  not  determined  by  the  nucleus. 

Still  farther,  the  size  of  the  cell  seems  to  be  determined  by 
the  cytoplasm  rather  than  by  the  nucleus.  The  indirect  or 
karyokenetic  division  of  the  nucleus  results  in  an  equal  division 
of  the  chromatic  substance.  After  the  division  has  taken 
place,  the  two-daughter  nuclei  are  for  a  considerable  period 
equal  in  size,  though  the  cell-bodies  in  which  they  lie  may  be 
very  unequal.  Likewise,  the  division  of  the  asters  is  always 
an  equal  division,  and  in  the  early  stages  of  karyokinesis  the 
two  asters  are  always  equal  in  size.  Yet  in  these  very  stages 
in  which  the  nuclei  and  the  asters  are  equal  in  size,  the  lobing 
of  the  cytoplasm  may  show  beyond  doubt  that  the  division  of 
the  cell-body  is  to  be  very  unequal.  I  believe,  therefore,  that 
neither  the  nuclei  nor  the  asters  determine  the  initial  size  of 

fertilization  ("  l^efruchtung,"  p.  469),  mentions  the  fact  that  he  fertilized  ova  of 
one  genus  of  sea-urchin  with  the  sperm  of  another,  from  which  cross  a  larval 
form  developed  which  was  intermediate  in  character  bet\yeen  the  two  genera. 
The  cleavage,  however,  was  purely  maternal,  thus  indicating  that  it  was  not 
influenced  by  the  sperm  nucleus.  He,  therefore,  concludes  that  the  process  of 
cleavage,  to  all  appearances  at  least,  is  not  directed  by  the  nucleus. 


34  BIOLOGICAL   LECTURES. 

the  cells  which  are  formed  by  division  ;  it  is  determined  rather 
by  the  general  cytoplasm.  In  the  later  stages  of  karyokinesis, 
after  the  lobing  of  the  cytoplasm  has  indicated  the  size  of  the 
daughter  cells,  but  sometime  before  the  division-wall  is  formed, 
the  asters  become  unequal  in  size  if  the  division  is  to  be  an 
unequal  one,  and  by  the  time  that  the  division-wall  is  formed 
the  asters  are  proportional  in  size  to  the  daughter  cells  in 
which  they  lie.  At  a  considerably  later  period  the  nuclei 
become  proportional  in  size  to  the  cells  in  which  they  are 
found. 

In  Crepidula,  therefore,  I  believe  it  is  certain  that  the  direc- 
tion of  the  cleavage,  as  also  the  position,  the  shape  and  the 
size  of  the  resulting  cells  are  not  directly  governed  by  the 
nucleus.  These  definite  forms  of  cleavage  which  are  so 
excellently  exemplified  in  Crepidula  are  inherited  as  certainly 
as  any  definite  adult  structures  are,  and  if  they  are  not 
under  nuclear  control,  these  hereditary  tendencies  must  be 
transmitted  through  the  cytoplasm. 

Of  course,  it  may  be  urged  that  there  is  some  unknown  and 
invisible  influence  emanating  from  the  nucleus  which  controls 
all  the  processes  of  cell  life.  In  the  nature  of  the  case  such 
an  assertion  cannot  be  affirmed  nor  denied  on  the  ground  of 
observation,  and  it  seems  to  me  sufficient  to  urge  in  reply  that 
we  should  believe  things  are  what  they  seem  unless  we  are 
compelled  to  believe  differently.  Many  of  the  processes  of 
cell  life  seem  to  be  controlled  by  the  cytoplasm  more  inti- 
mately than  by  the  nucleus  ;  so  far  as  we  can  observe,  all 
cytoplasm  comes  from  pre-existing  cytoplasm,  just  as  all 
nuclei  come  from  previous  nuclei.  We  know  that  the  cyto- 
plasm from  both  the  father  and  mother  are  represented  in 
every  stage  of  fertilization,  and  it  is  unnecessary  and  therefore 
unscientific  to  assume  that  the  nucleus  controls  all  the 
processes  of  cell  life,  and  that  the  heritable  characters  of  the 
cytoplasm  are  transmitted  only  through  the  nucleus. 

If,  in  stating  my  objections  to  the  view  held  by  the  vast 
majority  of  the  biologists  of  the  present  day,  I  may  seem  to 
have  denied  the  importance  of  the  nucleus  while  empha^zing 
the  importance  of  the  cytoplasm,  I  would  wish  to  say,  in  con- 


THE   FERTILIZATION  OF   THE    OVUM.  35 

elusion,  what  has  been  said  several  times  already,  that  I  con- 
sider both  cytoplasm  and  nucleus  essential  constituents  of  the 
cell,  and  therefore  one  cannot  be  said  to  be  more  important 
than  the  other.  In  all  the  phenomena  of  cell  life, — growth, 
regeneration,  fertilization,  division,  the  building  of  the  organ- 
ism, the  transmission  of  heritable  characters,  —  both  nucleus 
and  cytoplasm  take  part,  though  probably  not  always  an  equal 
part.  The  entire  cell  is  still  the  ultimate  independent  unit  of 
organic  structure  and  function. 


THIRD    LECTURE. 


ON    SOME    FACTS   AND    PRINCIPLES   OF   PHYSIO^ 
LOGICAL    MORPHOLOGY. 

JACQUES  LOEB. 

In  this  address  I  shall  give  a  short  account  of  a  series  of 
experiments  which  were  undertaken  in  order  to 
determine  the  causes  of  animal  forms.  Some  of 
the  results  of  these  investigations  have  already 
been  published. ^  Among  others,  which  are  new, 
are  experiments  upon  the  artificial  production  of 
double  and  multiple  monstrosities  from  one  ovum  ; 
in  the  sea-urchin. 


I.    Heteromorphosis. 

If  we  look  at  an  animal  we  perceive  that  its 
various  organs  are  arranged  in  a  definite  way. 
From  our  shoulders  originate  arms,  and  from  our 
hips  legs,  but  we  never  see  that  legs  grow  out 
from  the  shoulders  or  arms  from  the  hips.  In 
the  lower  animals  there  exists  the  same  definite  [ 
arrangement  of  parts. 

Fig.  I  is  a  diagram  of  a  hydroid  Antennularia, 
which  is  pretty  common  at  Naples.  From  a 
bundle  of  roots  or  stolons  a  perfectly  straight 
stem  arises  to  a  height  of  six  inches  or  more. 
From  this  main  stem  originate,  in  regular  suc- 
cession, very  short  and  slender  branches,  which 
carry  polyps  on  their  upper  sides. 

In  this  case  we  never  find  that  a  root  originates 
at  the  apex,  or  in  the  place  of  a  branch,  or  that 
polyps    originate    at    the    lower   side   of    a    branch 


1  Untersuchiingen  ziir  physiologischen  Morphologie  der  Thiere.     I,  Heteromor- 
phosis, WUrzburg,  1891.     II,  Organbildung  und  Wachsthum,  Wiirzburg,  1892. 


38  BIOLOGICAL   LECTURES. 

physiologist  the  question  arises :  What  are  the  circumstances 

which   determine  that  only  one  kind    of  organs   originate   at 

certain  places  in  the   body  ?     I  conceived  that  the  answer  to 

this  question  might  be  obtained  by  finding  out 

whether    or    not    it    was   possible  to   make  any 

desired  organ  of  an  animal  grow  at  any  desired 

place.     In  case  of    success,   the  question  to  be 

decided  was  whether  the  same  circumstances  by 

which  we  can  change  the  arrangement  of  organs 

experimentally  determine  also    the  arrangement 

of  organs  in  the  natural  development. 

If  we  cut  out  a  piece  (Fig.  2)  of  an  Antennu- 

laria,  and  hang  it  up  vertically  in  the  water,  the 

apical  end  b  above  and  the  root  end  a  below,  we 

find  that  after  a  few  days  the  root  end  a  forms 

little  roots,  r,  which  grow  downward, 

and  the  apical  end,  b,  forms  a  new 

apex,  c. 

If  we  cut  out  a  similar  piece  and 

hang  it  upside   down  (Fig.   3),    the 

root    end   ^,   which  now    is    above, 

forms  a  new  apex,  ac,  and  the  apical 

end  by  which  is  below,  forms  roots. 
Fig.  2.  ^  ,  , 

In   such   an  apex  the   arrangement 

of  organs  is  just  the  same  as  in  the  normal 
animal,  namely,  branches  growing  obliquely 
upward  bearing  polyps  on  their  upper  sides.  We 
are,  therefore,  able  to  substitute  a  root  for  an 
apex  and  an  apex  for  a  root.  I  have  called  this 
substitution  of  one  organ  for  another  hetero- 
morphosis.  If  we  place  the  cut-out  piece  of 
Antennularia  horizontally  instead  of  vertically, 
something  still  more  remarkable  happens,  namely, 
the  branches  on  the  lower  side  suddenly  begin  to 
grow  vertically    downward,   and    the    outgrowing  ^^"  ^' 

parts  are  no  longer  branches  but  roots,  rr,  Fig.  4.  This  we  can 
prove  by  their  physiological  reactions,  for  the  roots  fix  them- 
selves to  the  surface  of  solid  bodies,  for  instance,  the  glass  of 


ON  PHYSIOLOGICAL   MORPHOLOGY. 


39 


the  aquarium,  while  the  stems  never  show  any  reaction  of  this 
kind.  These  new  parts  growing  out  from  the  branches  of 
the  under  side  of  the  stem  attach  themselves  to  solid  bodies, 
if  we  bring  them  in 
contact  with  the  same. 
Moreover,  they  are  pos- 
itively geotropic  (that 
is,  they  grow  toward 
the  centreof  theearth), 
while  the  branches 
never  show  any  pos- 
itive geotropism.  The 
branches  on  the  upper 
side  are  not  trans- 
formed into  roots. 
They  either  perish  or  give  rise  to  very  long,  slender,  perfectly 
straight  stems  (b,  Fig.  4),  which  grow  vertically  upward. 
These  stems,  as  a  rule,  are  too  slender  to  bear  branches, 
but  at  parts  of  the  upper  surface  of  the  main  stem  there 
originate  new  stems  (<:,  Fig.  4)  which  grow  vertically  upward 
and  produce  the  typical  little  branches  with  polyps. 

If  we  bring  the  stem  into  an  oblique  position  (Fig  5),  with 
the  apex  b  upward,  from  every  element  of  the  main  stem  new 


Fig.  4. 


Stems  and  roots  may  originate,  but  with  this  difference,  stems 
always  originate  from  the  upper  side  of  an  element  and  roots 
from  its  lower  side.     But  if  we  place  the  stem  in  an  oblique 


40 


BIOLOGICAL   LECTURES. 


position  (Fig.  6),  with  the  root  end  above,  the  branches  on  the 
under  side  grow  out  as  roots  and  at  the  upper  end,  a  stem 
arises  as  usual. 

What  circumstances  have  all  these  experiments  in  common  ? 
These  two  :  stems  always  originate  from  the  upper  end  or  side 
of  an  element,  and  roots  always  originate  from  the  lower  side 
or  end  of  the  same  element.  These  facts  can  be  explained 
only  through  the  assumption  that  gravitation,  in  this  case, 
determines  the  place  of  origin  of  organs. 

Now  we  may  ask  whether  the 
action  of  this  force,  gravitation, 
produces  the  natural  arrangements 
of  parts,  i.  r.,  roots  growing  only  at 
the  base  of  the  stem  and  never  at 
the  apex  or  in  the  place  of  a  branch. 
I  think  that  it  does.  By  reason  of 
its  negative  geotropism,  the  stem 
grows  vertically  upwards.  Gravita- 
tion does  not  permit  roots  to  arise 
at  any  place  except  the  under  side 
of  the  organs,  and  that,  in  the 
normal  position,  is  the  base  of  the 
stem.  The  same  force  determines 
that  polyps  can  originate  only  at 
the  upper  side  of  branches,  and  so 
the  main  arrangement  of  organs  is 
brought  about  by  gravitation.  But 
how  does  gravitation  determine  that 
roots  grow  at  the  upper  and  stems 
at  the  under  side  t  This  is  a  question  to  which  I  shall  return 
later. 

Fig.  7  is  a  drawing  of  a  case  of  heteromorphosis  in  Margeliss, 
a  hydroid  common  at  Woods  Holl. 

If  we  cut  off  a  stem,  or  a  small  piece  of  a  stem,  and  place  it 
in  a  dish  containing  sea  water,  and  protect  it  carefully  from 
every  motion,  a  curious  change  takes  place  in  the  organism. 
Almost  all,  and  in  some  cases  all  of  the  stems  which  touch 
the  glass  begin  to  give  rise  to  roots  that  spread  out  and  very 


Fig.  7. 


ON  PHYSIOLOGICAL   MORPHOLOGY.  41 

soon  cover  a  large  area  of  the  glass.  In  this  way  the  apical 
end  of  a  stem  may  continue  to  grow  as  a  totally  different 
organ,  namely,  as  a  root.  Every  organ  not  in  contact  with 
some  solid  body  gives  rise  to  polyps.  Even  the  main  root,  if 
not  in  contact  with  a  solid  body,  no  longer  grows  as  a  root,  but 
gives  rise  to  a  great  number  of  small  polyps  which  appear  at 
the  end  of  long  stems.  Fig.  7,  which  Mr.  Tower  was  kind 
enough  to  draw  for  me,  shows  a  branch  which  formed  roots 
at  its  apex  and  polyps  at  its  roots  in  this  way.  The  stem 
touched  the  bottom  of  the  dish  with  the  apical  ends,  a,  b,  c  and  d. 
All  these  ends  gave  rise  to  roots.  From  the  upper  side  of  the 
original  root,  r,  which  was  not  in  contact  with  the  glass,  later 
on  small  polyps,  //,  grew  out.  Every  place  which  was  in  con- 
tact with  solid  bodies  gave  rise  to  roots,  and  every  place  which 
was  in  contact  with  sea  water  gave  rise  to  polyps. 

This  is  not  the  only  species  of  hydroid  found  at  Woods  Holl 
in  which  such  forms  of  Heteromorphosis  can  be  produced. 
Another  form,  Pennaria,  is  just  as  favorable.  In  Pennaria  I 
succeeded  repeatedly  in  producing  roots  at  both  ends  of  a 
small  stem  that  bore  no  polyps.^ 

What  circumstances  are  common  in  these  experiments  on 
Margelis  and  Pennaria }  Organs  brought  into  contact  with 
solid  bodies  continue  to  grow  as  roots,  if  they  grow  at  all. 
Organs  surrounded  on  all  sides  by  water  continue  to  grow  in 
the  form  of  polyps,  if  they  grow  at  all.      In  Margelis,  contact 

1  In  a  Tubularian  I  was  able  to  produce  the  opposite  case,  namely,  to  get  an 
animal  that  ended  at  both  ends  in  a  polyp  and  had  no  root.  Weismann  seems 
to  assume,  in  his  "  Germ  Plasm,"  that  the  latter  result  is  to  be  explained  by  the 
principle  of  natural  selection,  inasmuch  as  an  animal  without  polyps  could  not 
continue  to  live,  and  hence  it  would  be  impossible  to  produce  roots  at  both  ends. 
In  Pennaria  this  supposed  impossibility  was  realized.  One  may  say  that  these 
roots  in  Pennaria  may  give  rise  later  on  to  polyps.  In  the  special  case  that  I 
observed  they  did  not,  although  as  a  rule  they  do.  But  the  same  is  the  case  in 
Tubularia,  in  which  polyps  also  arise  from  the  roots.  It  might  be  said,  perhaps, 
that  the  formation  of  roots  in  Pennaria  is,  for  some  reason,  absolutely  necessary. 
But  it  is  just  as  easy  to  produce  polyps  at  both  ends.  Even  if  it  were  possible  to 
reconcile  these  facts  with  the  principles  of  natural  selection,  causal  or  physio- 
logical morphology  would  not  gain  thereby,  as  the  circumstances  that  determine 
the  forms  of  animals  and  plants  are  only  the  different  forms  of  energy  in  the 
sense  in  which  this  word  is  used  by  the  physicist,  and  have  nothing  to  do  with 
natural  selection. 


42  BIOLOGICAL  LECTURES. 

with  a  solid  body  plays  the  same  role  as  did  gravitation  in  the 
case  of  Antennularia.  In  what  way  the  contact  may  have  an 
influence  shall  be  mentioned  later.  We  may  add,  however, 
one  more  point.  In  Antennularia,  gravitation  not  only  deter- 
mines the  place  of  origin  of  the  various  organs,  but  also  the 
direction  of  their  growth  ;  the  stem,  growing  upward,  is  nega- 
tively geotropic,  the  root,  growing  downward,  is  positively 
geotropic.  In  Pennaria,  the  nature  of  the  contact  not  only 
determines  the  place  of  origin  of  the  various  organs,  but  also 
the  direction  of  their  growth.  If  we  bring  an  outgrowing 
polyp  of  Pennaria  into  contact  with  a  solid  body,  the  polyp 
begins  to  grow  away  from  the  body,  and  the  new  stem  is  very 
soon  nearly  perpendicular  to  the  part  of  the  surface  with  which 
it  came  into  contact. 

I  have  called  this  form  of  irritability  Stereotropism.  We 
may  speak  of  positive  Stereotropism  in  the  case  of  the  root, 
and  of  negative  Stereotropism  in  the  case  of  the  polyp. 

Here,  too,  it  may  be  asked  whether  contact  with  foreign 
bodies,  which  in  these  experiments  determined  the  arrange- 
ment of  the  various  organs,  may  not  have  the  same  effect  in 
the  natural  development  of  the  organism.  I  believe  that  such 
is  the  case.  Negative  Stereotropism  forces  the  polyps  to  grow 
away  from  the  ground  into  the  water,  and  so  parts  surrounded 
by  water  form  polyps  only.  Positive  Stereotropism  forces  roots 
in  contact  with  the  ground  to  grow  toward  it,  so  parts  in  con- 
tact with  the  ground  give  rise  to  roots  only.  Thus  it  happens 
that,  under  ordinary  circumstances,  in  the  animal  we  find  roots 
only  at  the  base  where  it  touches  the  ground.  In  other  hydroids 
the  place  of  origin  of  the  different  organs  is  determined  by 
light,  and  in  others  we  find  more  complicated  relations. 

It    may    appear   from   the   foregoing 

that  such  cases  of  heteromorphosis  are 

confined  to  hydroids,  but  such  is    not 

the    case.     We    find    similar    cases    in 

Timicates.     Ciona  intestinalis  (Fig.  8), 

a    solitary  ascidian,  has  eye-spots    around    the   two    openings 

into  the  pharyngeal  cavity,  a  and  b.     If  we  make  an  incision 

at  c,  eye-spots  are  formed  on  both  sides  of  the  incision. 


ON  PHYSIOLOGICAL  MORPHOLOGY. 


43 


While 
observed 
any  kind 


a 


II.    Polarization. 

the  foregoing  experiments  were  in  progress,  I 
that  in  many  animals  I  was  unable  to  produce 
of  heteromorphism.  These  animals  showed,  in 
regard  to  the  formation  of  organs,  a 
phenomenon  with  which  we  are  familiar  in 
a  magnet.  If  we  break  a  magnet  into 
pieces,  every  piece  has  its  north  pole  on 
that  side  which  in  the  unbroken  magnet 
was  directed  toward  the  north.  Likewise, 
there  are  animals  every  piece 
of  which  produces,  at  either     \\\\\|///Y 


Fig.  9. 


end,  that  organ  toward  which  ^ 
it  was  directed  in  the  normal 
condition.  We  may  speak  in 
such  cases  of  polarization. 
The  clearest  example  of  this 
I  found  in  an  actinian,  Ceri- 
anthus  membranacetis. 


Fig.  10. 


If  we  cut  a  rectangular  piece,  abed,  out  of  the  body- wall 
of  Cerianthus  (Fig.  9),  very  soon  new  tentacles  begin  to  grow 

out  of  this  piece,  but  only  from  the  side 
V\\\llMf  ab  (Fig.  10),  which  was  directed  toward  ^ 
WWU/////  the  oral  end  of  the  animal.  Nothing  of 
the  sort  occurs  in  the  side,  c  d,  or  ac, 
or  b  d.  The  production  of  tentacles 
takes  place  before  any  other  regeneration 
begins.  The  same  polarization  is  shown 
in  the  following  variation  of  the  preceding 
experiment  :  If  we  make  an  incision, 
abc  (Fig.  11),  into  the  body- wall  of  the  / 
actinian,  only  the  lower  lip,  be,  produces 
tentacles,  while  the  upper  lip,  a  e,  pro- 
duces none.  The  two  ends  heal  together 
in  such  a  way  that  one-half  of  a  mouth, 
with  its  surrounding  tentacles,  a  (Fig.  12), 
is  formed.     It  is  curious  to  see  how  these  tentacles  behave  if 


J 


Fig.  II. 


Fig.  12. 


44  BIOLOGICAL   LECTURES. 

we  offer  them  bits  of  meat.  They  endeavor  to  force  it  into 
the  new  oral  disc,  where  the  mouth  ought  to  be,  but  where  no 
mouth  exists,  and  only  after  a  struggle  of  some  minutes  give  up 
the  hopeless  attempt.  I  tried  in  every  possible  way  to  produce 
tentacles  in  the  aboral  end  of  a  piece  which  had  been  cut  out, 
but  without  success. 

Hydra  behaves,  as  regards  polarization,  a  little  differently 
from  Cerianthus.  If  we  make  an  incision  in  the  stem,  a 
whole  new  oral  pole  grows  out,  but  otherwise  it,  too,  shows 
polarization. 

A  good  many  animals,  so  far  as  is  yet  known,  reproduce 
only  the  lost  organ,  but  never  show  any  heteromorphism.  We 
see,  therefore,  that  while  in  some  animals  we  are  able  to  pro- 
duce heteromorphosis,  in  others  the  most  definite  polarization 
exists,  and  we  are  able  to  produce  regeneration  of  lost  parts 
only  in  the  arrangement  which  exists  in  the  normal  animal. 
In  this  case  we  must  assume  that  unknown  internal  conditions 
determine  the  arrangement  of  limbs. 

In  addition  to  examples  of  heteromorphosis  or  polarization 
occurring  separately,  we  find  cases  in  which  both  phenomena 
are  exhibited  by  the  same  animal.  If  we  cut  out  a  sufficiently 
large  piece  of  the  stem  of  Tubularia  mesembryanthemum,  and 
place  it  in  the  bottom  of  a  dish  of  water,  carefully  protected 
from  jarring,  the  anterior  end  of  the  piece  gives  rise  to  a  new 
polyp,  the  posterior  end  to  a  root  ;  but  if  we  hang  up  the  stem 
in  such  a  way  that  the  posterior  end  does  not  touch  the  surface 
of  the  glass,  and  is  sufficiently  provided  with  oxygen,  this  end, 
too,  produces  a  polyp,  and  we  have  a  true  case  of  heteromor- 
phosis. In  all  cases  the  polyp  at  the  oral  end  is  formed  first, 
and  a  relatively  long  time  (one  or  more  weeks)  elapses  before 
the  aboral  polyp  is  formed.  But  under  one  condition  I  could 
cause  the  stem  to  form  a  polyp  at  the  aboral  as  quickly  as  at 
the  oral  end,  namely,  by  inhibiting  or  retarding  the  formation 
of  the  oral  polyp.  This  could  be  done  readily  by  diminishing 
the  supply  of  oxygen  at  the  oral  end.  In  such  cases  the 
aboral  polyps  were  produced  nearly  as  quickly  as  the  oral 
polyps. 


ON  PHYSIOLOGICAL   MORPHOLOGY.  45 

III.    The  Mechanics  of  Growth  in  Animals. 

In  order  to  get  an  explanation  of  the  phenomena  of  organiza- 
tion we  must  ask,  What  are  the  physical  forces  that  determine 
the  formation  of  a  new  organ  t  We  know  that  the  ultimate 
sources  of  energy  for  all  the  functions  of  living  bodies  are 
chemical  processes.  The  question  is,  How  can  these  chemical 
forces  be  brought  into  relation  with  the  visible  changes  which 
take  place  in  the  formation  of  a  new  organ  .-*  The  answer  to 
this  question  is  to  be  obtained  by  a  knowledge  of  the  mechanics 
of  growth.  It  is  very  remarkable  that  the  mechanics  of  growth 
forms  almost  an  empty  page  in  the  history  of  animal  morphol- 
ogy and  physiology.  I  can  refer  here  only  to  the  few  experi- 
ments that  I  have  made  on  this  subject  ;  but  fortunately  the 
subject  has  been  worked  out  very  carefully  in  plants,  and  as 
my  experiments  show  that  the  conditions  for  growth  in  animals 
are,  to  a  certain  extent  at  least,  the  same  as  the  conditions  for 
growth  in  plants,  we  have  the  beginning  of  a  basis  for  work. 

A  brief  outline  of  the  manner  of  growth  in  plants  is  as  fol- 
lows :  Before  the  cell  grows  it  forms  substances  which  attract 
water  from  the  surroundings,  or,  as  the  physicist  expresses  it, 
it  forms  substances  which  determine  a  higher  osmotic  pressure 
within  the  cell  than  did  the  substances  from  which  they  origi- 
nate. The  walls  of  the  cell,  or  rather  the  protoplasmic  layer 
that  lines  the  cell  wall,  possesses  peculiar  osmotic  properties, 
in  consequence  of  which  it  allows  molecules  of  water  to  pass 
through  freely  while  remaining  resistant  to  the  passing  through 
of  the  molecules  of  many  salts  dissolved  in  the  water.  The 
result  is  that  when  substances  of  higher  osmotic  pressure  are 
formed  inside  the  cell,  water  from  the  outside  passes  in 
until  the  pressure  within  again  equals  the  pressure  without. 
The  cell-wall  becomes  stretched  and,  according  to  Traube, 
new  material  is  precipitated  in  the  enlarged  interstices, 
thus  rendering  growth  permanent.  This  method  of  growth  is 
most  conspicuous,  perhaps,  in  the  germinating,  seed.  The  rising 
temperature  in  spring  produces  in  the  seed  substances  of  higher 
osmotic  pressure  (with  greater  attraction  for  water)  than  the 
substances    from  which    they  originate.      The    result    is    that 


46  BIOLOGICAL    LECTURES. 

water  enters  the  seed ;  by  the  pressure  of  the  water  within  the 
cells  their  walls  are  stretched  out  and  the  seed  grows.  The 
chemical  and  osmotic  changes  are  the  sources  for  the  energy 
which  is  needed  to  overcome  the  resistance  to  growth. 

To  see  whether  I  could  determine  what  are  the  mechanical 
causes  of  growth  in  animals,  I  began  at  Naples  some  experi- 
ments on  Tubularia  mesembryanthemum.  I  chose  long  stems 
belonging  to  the  same  colony  and  distributed  them  in  a  series 
of  dishes  containing  sea-water  of  different  concentrations.  In 
some  of  the  dishes  the  concentration  had  been  raised  by  adding 
sodium  chloride,  and  in  others  it  had  been  lowered  by  adding 
distilled  water.  According  to  the  laws  of  osmosis  the  amount 
of  water  contained  in  the  cells  of  these  tubularians  differed 
with  the  concentration  of  the  sea-water,  the  amount  being 
greatest  in  the  most  diluted  solution  and  least  in  the  most 
concentrated    solution.      If    now  in    reality  the   mechanics    of 


/  1  3 

DiL  ifjed  S^A  -  ¥fAr£P 


Fig.  n. 


growth  are  the  same  for  animals  as  for  plants,  it  must  result 
that  the  more  diluted  the  sea-water  the  more  rapid  would  be 
the  growth  in  the  tubularian  stem.  Of  course,  at  last,  a  limit 
is  reached  where  the  water  begins  to  have  a  poisonous  effect. 
It  was  found,  indeed,  that  within  certain  limits  of  concentra- 
tion the  increase  in  the  length  of  the  stems  during  the  same 
period  was  greatest  in  the  most  diluted  and  least  in  the  most 
concentrated  sea-water.  It  is  remarkable  that  the  maximum  of 
growth  took  place  not  in  sea-water  of  normal  concentration, 
but  in  more  diluted  sea-water,  though  that  of  course  may  not 
be  the  case  in  all  animals.  The  following  curve  (Fig.  13)  will 
give  an  idea  of  the  dependence  of  growth  upon  the  concentra- 
tion of  the  sea-water  in  Tubularia.     The  values  for  the  amount 


ON  PHYSIOLOGICAL    MORPHOLOGY.  47 

of  sodium  chloride,  in  100  cubic  centimetres  of  sea- water,  are 
represented  on  the  axis  of  the  abscissa,  the  values  for  the 
increase  in  growth  on  the  ordinate  axis. 

These  and  similar  experiments,  which  on  account  of  lack  of 
time  I  cannot  mention  here,  show  that  growth  in  animals  is  de- 
termined by  the  same  mechanical  forces  that  determine  growth 
in  plants.  An  obstacle  to  such  a  conclusion  seems  to  lie  in 
the  fact  that  many  plant  cells  have  solid  walls,  while  such  is 
not  the  case  in  most  animal  cells.  But  the  solid  cell-wall  does 
not  determine  the  peculiar  character  of  growth.  This  charac- 
ter is  determined  first,  by  chemical  processes  within  the  cell, 
which  result  in  a  higher  osmotic  pressure,  and,  secondly,  by 
the  osmotic  qualities  of  the  outer  layer  of  protoplasm,  which 
allows  water  to  pass  through  freely,  but  does  not  allow  all  salts 
dissolved  in  it  to  do  the  same.  Both  these  qualities  are  inde- 
pendent of  the  solid  cell-wall,  and  I  see  no  reason  why  the 
animal  cell  should  not  agree  in  these  two  salient  features  with 
the  plant  cell. 

In  order  that  the  foregoing  explanation  of  the  mechanism  of 
growth  in  the  animal  cell  might  be  based  only  upon  known 
processes,  it  was  necessary  to  find  out  whether,  indeed,  in  case 
of  growth,  chemical  processes  of  such  a  character  take  place 
that  there  are  formed  substances  of  higher  osmotic  pressure 
than  those  from  which  they  originate.  Every  one  knows  that 
by  practice  our  muscles  increase  in  size.  No  satisfactory 
explanation  of  this  fact  has  been  given.  If  my  interpretation 
of  the  method  of  growth  was  correct,  I  must  expect  that  during 
activity  there  are  formed  in  the  muscle  substances  which  deter- 
mine a  higher  osmotic  pressure  than  those  from  which  they 
originate.  This  is  exactly  the  case.  Ranke  had  already  shown 
that  the  blood  of  a  tetanized  frog  loses  water  and  that  this 
water  is  taken  up  by  the  muscles.  In  experiments  which  were 
carried  on  by  Miss  E.  Cooke  in  my  laboratory,  we  were  able  to 
show  directly  that  during  activity  the  osmotic  pressure  inside 
the  cell-wall  is  raised.  We  determined  the  concentration  of  a 
solution  of  Na  CI,  or  rather  of  a  so-called  Ringers  mixture,  in 
which  the  gastroconemius  of  a  frog  neither  lost  nor  took  up 
water.     We  found  that  while  this  concentration  for  the  resting 


48  BIOLOGICAL  LECTURES. 

gastroconemius  was  about  075  per  cent,  to  0.85  per  cent.,  for 
the  gastroconemius  that  had  been  tetanized  from  20  to  40 
minutes  it  varied  from  1.2  per  cent,  to  1.5  per  cent. 

This  increase  of  osmotic  pressure  inside  the  muscle  cell 
leads,  during  normal  activity,  to  a  taking  up  of  water  from  the 
blood  and  lymph,  and  the  consequence  is  an  increase  in  volume. 
The  same  muscle,  as  soon  as  it  ceases  to  be  exercised,  begins 
to  decrease  in  size.  Activity,  therefore,  plays  the  same  role 
in  the  growth  of  a  muscle  that  the  heat  of  spring  plays  in  the 
growth  of  the  seed. 

Upon  endeavoring  to  determine  whether  the  function  of  seg- 
mentation, like  other  functions  of  growth,  is  influenced  by 
the  amount  of  water  contained  in  the  cell,  I  found  that  by 
decreasing  the  amount  of  water  in  the  ovum  of  the  sea-urchin 
segmentation  is  retarded,  and  that  by  using  a  sufficiently  high 
concentration  of  sea-water  it  may  be  stopped  entirely.  There- 
fore the  amount  of  water  contained  in  the  cell  plays  still 
another  role  in  the  process  of  organization  and  influences  the 
process  of  cell  division. 

IV.    The  Artificial  Production  of  Double  and  Multiple 
Monstrosities  in  Sea-Urchins. 

The  idea  that  the  formation  of  the  vertebrate  embryo  is  a 
function  of  growth  has  been  made  the  basis  of  the  embryo- 
logical  investigations  of  His.  In  a  masterly  way,  His  has 
shown  how  inequality  of  growth  determines  the  differentiation 
of  organs.  In  the  blastoderm  of  a  chick,  for  example,  the  first 
step  in  the  formation  of  the  embryo  is  a  process  of  folding. 
There  originates  a  head  fold,  a  tail  fold,  a  medullary  groove 
and  the  system  of  amniotic  folds.  According  to  His,  all  these 
processes  of  folding  are  due  simply  to  inequalities  of  growth, 
the  centre  of  the  blastoderm  growing  more  rapidly  than  the 
periphery.  It  can  be  shown,  very  simply,  that  such  a  process 
of  unequal  growth  must,  indeed,  lead  to  the  formation  of  exactly 
such  a  system  of  folds  as  we  find  in  the  blastoderm  of  a  chick. 
If  we  take  a  thin,  flat  plate  of  elastic  rubber,  such  as  is  used 
for  medical  purposes,  and  lay  it  on  a  drawing-board,  we  can 


ON  PHYSIOLOGICAL   MORPHOLOGY.  49 

imitate  the  stronger  growth  in  the  centre  by  sticking  two  tacks 
into  the  middle  of  the  rubber,  a  short  distance  apart,  and 
then  pulling  them  in  opposite  directions.  In  this  way  we 
imitate  unequal  growth,  the  centre  growing  faster  than  the 
periphery.  If  we,  then,  fix  the  tacks  in  the  drawing-board, 
so  that  the  rubber  in  the  middle  remains  stretched,  we 
get  the  same  system  of  folds  shown  by  the  embryo  of  a 
chick.  I  mention  this  way  of  demonstrating  the  effects  of 
unequal  growth  as  the  ideas  of  His  are  still  doubted  by  some 
morphologists. 

His  raised  the  question,  Why  is  growth  different  in  different 
parts  of  the  blastoderm  }  But  instead  of  trying  to  answer  it 
from  the  physiological  standpoint  he  answered  it  from  the 
anatomical  standpoint.  According  to  His,  the  different  regions 
of  the  unsegmented  ovum  correspond  already  to  the  different 
regions  of  the  differentiated  embryo.  But  this  so-called  theory 
of  preformed  germ-regions  gives  no  answer  to  the  question, 
Why  do  some  parts  of  the  embryo  grow  faster  than  others  } 
Nevertheless,  it  is  not  necessarily  in  opposition  to  the  theory 
of  growth  that  I  offered  in  the  preceding  chapter.  Starting 
with  the  idea  of  His,  we  may  well  imagine  that  the  different 
regions  of  the  ovum  are  somewhat  different  chemically,  and 
that  these  chemical  differences  of  the  different  germ-regions 
determine  the  differences  of  growth  in  the  blastoderm.  Thus 
the  phenomena  of  heteromorphosis  would  show  that,  in  some 
animals  at  least,  the  arrangement  of  preformed  germ-regions 
may  be  changed  by  gravitation,  light,  adhesion,  etc. 

But,  from  the  standpoint  of  causal  morphology,  it  must  be 
asked  what  determines  the  arrangement  of  the  different  germ- 
regions  in  the  ovum.  If  we  answer  ''heredity,"  causal  mor- 
phology can  make  no  use  of  such  an  explanation.  Our  blood 
has  the  temperature  of  about  37°,  but  although  our  parents  had 
the  same  temperature  its  heat  is  not  inherited,  but  is  the  result 
of  certain  chemical  processes  in  our  tissues.  Still  it  may  be 
possible  that  the  molecular  forces  of  the  chemically  different 
substances  of  the  ovum  determine  a  separation  of  these 
substances  and  at  the  same  time  the  chief  directions  of  the 
future  embryo. 


50  BIOLOGICAL   LECTURES. 

Driesch  has  shown  ^  that  by  shaking  a  sea-urchin's  ^gg  in  the 
four-celled  stage  the  four  cells  may  be  separated,  and  each  one 
be  capable  of  giving  rise  to  a  complete  embryo,  which  is  only 
different  in  size  from  the  normal  em^bryo.  If  the  theory  of 
preformed  germ-regions  with  its  later  modifications  were  true, 
we  ought  to  expect  that  every  one  of  the  isolated  cells  would 
give  rise  to  one-fourth  of  an  embryo.  But  it  has  been  said 
that  the  artificial  isolation  of  one  cleavage  cell  causes  a  process 
of  post  generation  or  regeneration.  Driesch,  moreover,  changed 
the  mode  of  the  first  cleavage  by  submitting  the  ovum  to  one- 
sided pressure.  In  this  way  the  nuclei  were  brought  into 
somewhat  different  places  from  those  they  would  have  held  in 
the  case  of  normal  segmentation.  Still,  normal  embryos 
resulted.  One  might  object  again  that  the  preformation  of 
the  germ-regions  existed  in  the  protoplasm,  and  not  in  the 
nucleus.  I  have  made  a  series  of  experiments  to  the  results 
of  which  these  objections  cannot  be  made.  I  shall  describe 
these  experiments  somewhat  fully,  as  they  have  not  yet 
been  published,  though  I  cannot  enter  into  details  at  this 
place. 

I  brought  eggs  of  a  sea-urchin,  within  ten  to  twenty  minutes 
after  impregnation,   into  sea-water   that   had   been  diluted   by 

the  addition  of  about  lOO  per 
cent,  distilled  water.  In  this 
solution  the  eggs  took  up  so 
much  water  that  the  mem- 
brane (;;/,  Fig.  14)  burst  and 
part  of  the  protoplasm  escaped 
in  the  form  of  a  drop  {b,  Fig. 
14),  which  often,  however,  re- 
mained in  connection  with  the  protoplasm  inside  the  membrane 
after  the  eggs  were  brought  back  into  normal  sea-water. 
These  eggs  gave  rise  to  adherent  twins,  the  ejected  part  of  the 
protoplasm,  b,  as  well  as  the  part  remaining  inside  the  mem- 
brane, developing  into  a  normal  and  perfectly  complete  embryo. 
The  part  of  the  protoplasm  which  at  first  had  connected 
the  two   drops,  formed    the   part   where    the   twins    remained 

'^  Zeitschrift  f.  luissensch.  Zoologie,  Vol.  LI  1 1  and  LV. 


Fig.  14. 


ON  PHYSIOLOGICAL   MORPHOLOGY.  51 

grown  together.  Of  course,  it  often  happened  that,  by 
accident  or  rapid  movement,  the  twins  were  separated,  and 
they  then  developed  into  perfectly  normal  single  embryos. 
Since  we  cannot  assume  that  in  every  case  the  same  part 
of  the  protoplasm  escapes,  we  must  conclude  that  every 
part  of  the  protoplasm  may  give 
rise  to  fully  developed  embryos 
without  regard  to  preformed 
germ-regions.  In  many  eggs  a 
repeated  outflow  of  the  proto- 
plasm takes  place  (Fig.  15).     In 

such  cases    each    of   the  drops 

•  .  Fig.  15. 

of  the  protoplasm  may  give  rise 

to    an    embryo,    and    I    obtained    not   only    double    embryos, 

but  triplets  and  quadruplets  all  grown  together. 

In  order  to  understand  these  experiments  more  fully,  let  us 

follow  out   the   history   of   development   in   these   double   and 

multiple   monstrosities.     The   ova  were   put   into   the   diluted 

sea-water  before  any  segmentation  had  taken  place  and  while 

they  had  still  but  one  nucleus.     When  parts  of  the  protoplasm 

flowed   out,  the   nucleus   either  remained   in   the   protoplasm, 

inside  of  the  membrane,  or  passed  out  with  the  part  that  was 

ejected.     Therefore,  at  first,  only  one  part  of  the  protoplasm 

contained  a  nucleus.     The  other  part  obtained  its  nucleus  by 

the  cleavage  which  took  place,  as  follows  :    In  case  the  nucleus 

had  remained  inside  the  membrane  (Fig.  16),  the  first  cleavage 

took  place  inside  the  membrane,  the 

cleavage  plane  being  always  at  right 

angles  to  the   common  diameter  of 

the  two  protoplasmic  drops  (Fig.  16). 

(Only  when  the  nuclear-spindle  had 

already  formed,   at  the  time  of  the 

bursting    of    the    membrane,    were 

there  exceptions   to    this    rule.)      A    peculiarity    of   the   first 

cleavage  was  that  the   protoplasm  was  always  divided   into  a 

larger  sphere  (I,  Fig.  16),  and  a  smaller  sphere  (II)  which  was 

connected  with  the  extra-ovate. 


52 


BIOLOGICAL   LECTURES. 


The  next  stage  was  a  normal  division  of   I  (Fig.  17),  and 
then  II,  divided  (Fig.  18),  the  cleavage  plane,  as  a  rule,  lying 


Fig.  18. 


in  the  extra-ovate.  In  this  way  the  extra-ovate  obtained  its 
nucleus,  receiving  in  this  case  but  one-fourth  of  the  whole. 
It  very  often  happens  that  the  extra-ovate  receives  its  nucleus 
later,  obtaining  in  that  case  a  still  smaller  fragment,  but,  never- 
theless, the  outcome  is  a  perfectly  normal  embryo.      Later  on 


the  division  takes  its  regular  course.  Fig.  19  shows  the  morula 
stage,  and  one  recognizes  already  the  double  monster.  Figs. 
20,  21  and   22   show  double,  triple    and   quadruple    gastrulae. 


Fig.  21. 


Fig.  22. 


ON  PHYSIOLOGICAL    MORPHOLOGY. 


53 


Figs.  23  and  24  represent  double  Plutei  and  Fig.  25   a  triple 
Pluteus. 

It  is  remarkable  that  the  development  of  these  monstrosities 
goes  on  nearly  at  the  same  rate  as  that  of  the  normal  embryo, 
provided  they  are  equally  well 
supplied  with  oxygen  and 
equally  protected  from  mi- 
crobes and  infusoria.  If  pre- 
formed germ-regions  deter- 
mined the  arrangements  of 
organs  in  the  embryo,  we 
ought  to  expect  that  these 
ruptured  ova  would  give  rise 
to  single  embryos,  with  a 
modified  arrangement  of 
limbs,  and  not  to  several 
embryos  with  normally  ar- 
ranged limbs.  Nevertheless, 
it  remains  true  that  the  de- 
velopment in  most  eggs  takes 
place   in   such  a  regular  and 


Fig.  23. 


typical  manner  that  it  seems  as  if  there  were  a  pre-arrangement 
of  some  kind.  But  it  is  perfectly  well  possible  that  this  pre- 
arrangement  consists  in  a  separation  of  different  liquid  sub- 
stances in  the  ovum  by  the  molecular  qualities  of  these 
liquids.  Such  a  separation,  of  course,  might  be  called  a 
preformation  of  germ-regions,  but  it  would  be  something 
totally  different  from  what  is  now  understood  by  that  term. 

V.    Theoretical  Remarks. 


I.  All  life  phenomena  are  determined  by  chemical  processes. 
This  is  equally  the  case  whether  we  have  to  do  with  the 
contraction  of  a  muscle,  with  the  process  of  secretion  or  with 
the  formation  of  an  embryo  or  a  single  organ.  One  of  the 
steps  that  physiological  morphology  has  to  take  is  to  show  in 
every  case  the  connecting  link  between  the  chemical  processes 
and  the  formation  of  organs.     I  have  tried  to  show  that  in  a 


54 


BIOLOGICAL   LECTURES. 


few  cases  at  least  this  connecting  link  was  to  be  sought  in  the 
changes  of  osmotic  pressure  determined  by  the  chemical  changes 
which  take  place  in  the  growing  organ. 

But  this  fact  alone  does  not  explain  why  it  is  that  we  get 
differences  in  the  forms  of  organs.  In  order  to  understand 
this  we  must  bear  in  mind  that  the  processes  of  growth  must 
necessarily  be  different  for  different  organs,  as  for  example  in 
the  formation   of  a  root,  and   the   formation   of  a   stem.     As 


Fig.  24. 


growth  is  a  process  in  which  energy  is  used  up  in  overcoming 
the  resistance  to  growth,  differences  of  growth  can  only  be 
determined  either  by  differences  in  the  amount  of  energy  set 
free  in  the  growing  organ  or  by  differences  in  resistance.  Dif- 
ferences in  the  energy  must  be  the  outcome  of  differences  in  the 
chemical  processes  which  determine  growth.  Therefore  we 
are  led  to  the  idea  that  differences  in  the  forms  of  different 
organs  must  be  determined  by  differences  in  their  chemical 


ON  PHYSIOLOGICAL    MORPHOLOGY. 


55 


constitution,  or,  if  the  chemical  constitutions  be  similar,  by 
differences  in  resistance  to  growth.  That  organs  which  differ 
in  shape  very  often  are  chemically  different  is  a  well  known 
fact.  The  formation  of  urea  in  the  liver  and  the  synthesis  of 
hippuric  acid  by  the  kidneys  are  the  consequences  of  chemical 
differences. 

In  this  way  we  are  led  through  the  mechanics  of  growth  to 
a   conclusion    which    forms    the   nucleus   of    Sachs'   theory  of 


Fig.  25. 

organization,  namely,  "  that  differences  in  the  form  of  organs 
are  accompanied  by  differences  in  their  chemical  constitution, 
and  that  according  to  the  principles  of  science  we  have  to 
derive  the  former  from  the  latter."  According  to  Sachs  there 
are  as  many  "  spezifische  Bildungsstoffe  "  in  a  plant  as  there 
are  different  organs. ^ 

1  J.  Sachs,  Stoffund  Form  der  PJlanzenorgane,  Gesammelte  Abhandlungen,  Vol. 
II,    1893. 


56  BIOLOGICAL   LECTURES. 

2.  In  adopting  the  theory  of  Sachs  and  applying  it  to 
animal  morphology,  we  must  avoid  a  mistake  very  often  made 
even  in  the  case  of  good  theories,  namely,  the  endeavor  to 
explain  special  cases  which  are  complicated  by  unknown 
conditions.  Huyghens  explained  by  his  theory  of  light  the 
phenomena  of  refraction,  but  he  could  not  and  did  not  attempt 
to  explain  the  sensations  of  color.  For  these  phenomena 
the  wave  theory  of  light  remains  true,  but  color  sensations 
depend  not  only  on  the  wave  motion  of  the  ether,  but  also 
on  the  peculiar  chemical  and  physical  structure  of  the  retina. 
I  think  it  perfectly  safe  to  say  that  every  animal  has  specific 
germ  substances,  and  that  the  germ  substances  of  different 
animals  differ  chemically.  Its  chemical  qualities  determine 
that  from  a  chick's  Qgg  only  a  chick  can  arise.  But  it  would 
be  a  mistake  and  a  falling  back  into  the  German  Natur- 
philosophie  to  attempt  at  present  an  explanation  of  how  the 
unknown  chemical  nature  of  the  germ  determines  all  the 
different  organs  and  characters  that  belong  to  the  species. 
For  instance,  the  yolk  sac  of  the  Fundulus  embryo  has  a  tiger- 
like coloration.  We  might  say  that  these  markings  may  be 
due  to  a  certain  arrangement  of  molecules  or  complexes  of 
molecules  (determinants),  which  later  on  give  rise  to  the  colored 
places  of  the  yolk  sac,  but  I  found  that  this  coloration 
originates  in  a  manner  much  more  simple.  The  pigment  cells 
are  formed  irregularly  on  the  surface  of  the  yolk.  The  pigment 
is  chemically  closely  related  to  haemoglobin,  and  so  its  forma- 
tion may  from  the  first  be  connected  with  the  formation  of  the 
blood  corpuscles.  But  the  arrangement  of  the  pigment  cells 
during  the  first  days  of  development  is  not  such  as  to  produce 
any  definite  markings.  They  lie  upon  the  walls  of  the  blood 
vessels  as  well  as  in  the  spaces  between  the  capillaries.  Later 
on,  however,  all  of  the  pigment  cells  have  crept  upon  the 
surface  of  the  neighboring  blood  vessels.  I  succeeded  experi- 
mentally in  showing  it  to  be  probable  that  some  of  the 
substances  contained  in  the  blood  determine  this  reaction. 
These  substances,  if  they  diffuse  from  the  blood  vessel  and 
touch  the  chromatophore,  make,  according  to  the  laws  of 
surface  tension,  the    protoplasm    of   the    chromatophore    flow 


ON  PHYSIOLOGICAL   MORPHOLOGY.  57 

towards  and  at  last  over  the  blood  vessel  and  form  a  sheath 
around  it,  while  the  gaps  between  the  blood  vessels  become 
empty  of  chromatophores.  In  this  way  the  chromatophores 
are  arranged  in  stripes,  and  changes  in  the  surface  tension,  and 
not  a  preformed  arrangement  of  the  germ,  determine  the 
marking.  We  do  not  know  what  processes  determine  the 
coloration  of  animals  which  owe  their  markings  to  interference 
colors,  but  the  task  of  deriving  such  a  coloration  in  the  adult 
from  a  similar  arrangement  of  molecules  in  the  germ  plasm 
would  prove  too  much  even  for  a  genius  like  Huyghens,  and 
without  the  possibility  of  such  a  derivation  the  theory  is  of 
no  use. 

3.  The  reasons  why  roots  grow  on  the  under  side  of  the 
stem  of  Antennularia  and  stems  on  the  upper  side,  can  only  be 
given  when  the  special  physical  and  chemical  conditions  inside 
the  stem  of  Antennularia  have  been  worked  out.  At  present 
we  can  only  think  of  possibilities.  It  is  possible  that  the 
hypothetical  root  substances  of  Sachs  may  have  a  greater 
specific  gravity  than  the  substances  which  form  stems,  and 
therefore  take  the  lowest  position  in  the  cell.  Since  outgrowth 
can  take  place  only  at  the  free  surface  of  a  stem  or  branch, 
roots  could  grow  only  at  the  under  side  and  stems  only  at  the 
upper  side  of  an  element.  But  there  are  still  other  possibilities 
which  we  must  omit  here.  In  the  case  of  Margelis  and  other 
hydroids,  it  might  happen  that  contact  with  solid  bodies 
produced  an  increase  of  surface  in  the  touched  elements  in 
case  they  contained  specific  root  substances,  while  the  opposite 
took  place  in  the  case  of  elements  containing  polyp  substances. 
The  consequence  would  be  an  increase  in  the  surface  of  the 
roots  if  they  came  into  contact  with  solid  bodies,  while  polyps 
only  would  grow  out  in  the  opposite  direction.  I  found,  indeed, 
in  some  forms  at  Naples  that  roots  of  hydroids  which  grew  free 
in  the  water  began  to  grow  much  faster  and  to  branch  off  more 
abundantly  when  brought  into  contact  with  solid  bodies.  But 
in  these  cases  we  must  wait  with  our  attempts  at  explanation 
until  the  physical  and  chemical  conditions  for  the  form  are 
worked  out.  For  the  same  reasons  I  will  not  go  into  a  discus- 
sion  of  the  question  of  what  determines  the  polarization  of 


58  BIOLOGICAL   LECTURES. 

animals  like  Cerianthus.  It  may  suffice  to  suggest  the  possi- 
bility that  in  polarized  animals  the  tissues  or  cells  may 
have  such  a  peculiar  structure  as  to  allow  the  specific 
formative  substances  to  migrate  or  arrange  themselves  only 
in  one  direction,  while  in  cases  of  heteromorphosis  migra- 
tion or  arrangement  in  every  or  in  several  directions  is 
possible. 

4.  The  ovum  of  a  sea-urchin  under  normal  conditions  gives 
rise  to  but  one  embryo.  This  circumstance  is  due  simply  to 
the  geometrical  shape  of  the  protoplasm,  which,  under  normal 
conditions,  is  that  of  a  sphere.  When  we  make  the  eggs 
burst,  the  protoplasm  outside  the  (t^g  membrane  and  that 
which  remains  within  it  assume  spherical  forms,  by  reason  of 
the  surface  tension  of  the  protoplasm.  When  this  happens, 
as  a  rule,  we  get  twins,  if  two  separate  segmentation  cavities 
are  formed,  and  only  one  embryo,  if  both  cavities  communi- 
cate with  one  another.  Whether  the  first  or  the  second  case 
will  happen  depends  upon  the  molecular  condition  of  the  part 
of  the  protoplasm  connecting  the  two  drops.  Therefore,  the 
number  of  embryos  which  come  from  one  ovum  is  not  deter- 
mined by  the  preformation  of  germ  regions  in  the  protoplasm, 
or  nucleus,  but  by  the  geometrical  shape  of  the  ovum  and 
the  molecular  condition  of  the  protoplasm,  in  so  far  as  these 
circumstances  determine  the  number  of  blastulae.  In  my 
experiments,  I  got  double  or  triple  embryos  when  the  ovum 
formed  a  double  or  triple  sphere,  as  every  sphere  determines 
a  blastula.  In  Driesch's  experiments,  one  single  cell  of  the 
four-cell  stage  necessarily  formed  a  whole  embryo  after  it  had 
been  isolated,  as  it  assumed  the  shape  of  a  single  sphere  or 
ellipsoid.  Of  course,  there  must  be  a  limit  to  the  number  of 
embryos  that  can  arise  from  one  ^%g\  but  the  limit  is  not  due 
to  any  preformation,  but  to  other  circumstances,  the  chief 
one  being  that  with  too  small  an  amount  of  protoplasm  the 
formation  of  a  blastula  —  from  merely  geometrical  reasons, 
as  there  must  be  a  minimum  size  for  the  cleavage  cells,  — 
becomes  impossible.  Without  the  formation  of  the  blastula, 
of  course  it  is  not  possible  to  get  the  later  stages  which 
are  determined  by  the  blastula. 


ON  PHYSIOLOGICAL   MORPHOLOGY.  59 

5.  The  formation  of  the  embryo  begins  with  the  formation 
of  the  gastrula.  The  hollow  sphere  (the  blastula,  Fig.  26) 
begins  to  fold  at  one  place  {ciy  c,  b,  Fig.  26),  and  an  invagina- 
tion takes  place  (Fig.  27).  The  formation  of  the  fold  {ciy  c,  b, 
Fig.  27)  is  due,  undoubtedly,  to  unequal  growth.  The  fact 
that  invagination,  and  not  evagination  (Fig.  28),  takes  place 


Fig.  27. 

depends  upon  other  conditions.  So  far  as  the  first  phenom- 
enon is  concerned,  there  are  different  possibilities  by  which 
unequal  growth  may  lead  to  a  process  of  invagination.  It  is 
possible,  for  instance,  that  the  part  c  (Fig.  26),  between  a  and 
bf  may  begin  to  grow  more  rapidly  than  the  rest.  But  such 
an  unequal  growth  can  only  be  the  outcome  of  a  chemical 
difference  between  the  parts  a,  c,  b,  and  the  rest.  Such  a 
distribution  of  chemically  different  material  exists  in  the 
blastula  which  originates  from  the  extra  ovate,  as  well  as  in 
the  one  which  develops  within  the  membrane.  In  the  normal 
ovum  this  distribution  of  material  finds,  perhaps,  its  first  mor- 
phological expression  in  the  formation  of  micromeres.  But 
Driesch  has  shown  that  all  possible  variations  in  the  formation 
of  micromeres  may  occur  without  affecting  the  formation  of 
the  embryo.  A  necessary  condition  for  the  formation  of  the 
embryo  is  the  chemical  differentiation  which  leads  to  unequal 
growth;  but  whether  this  differentiation  exists  from  the  first, 
or  whether  it  takes  place  in  the  eight  or  the  sixteen  or  the 
sixty-four-cell  stage  is  of  minor  importance.  In  order  to 
demonstrate  this  I  made  eggs  burst  in  the  two,  four,  sixteen, 
and  sixty-cell  stages.  In  all  cases  except  the  sixty-cell  stage 
I  produced   the   doublets,   triplets,   etc.      The    only   condition 


6o  BIOLOGICAL   LECTURES. 

necessary  was  that  one  part  of  the  protoplasm  should  flow  out. 
The  chief  facts  for  causal  morphology  are  the  chemical  differ- 
ences and  the  local  distribution  of  the  chemically  different 
material  by  molecular  forces. 

In  regard  to  the  question  why  under  normal  conditions 
the  entoderm  is  pushed  inside  the  segmentation-cavity 
I  wish  to  direct  attention  to  a  point  that,  as  far  as  I 
know,  has  not  yet  been  considered.  The  sea-urchin's  ^z%y 
during  the  first  stages  of  development,  has  a  higher  specific 
gravity  than  the  sea-water.  In  the  blastula  stage,  however, 
its  specific  gravity  decreases  and  the  ^gg  begins  to  float  and 
comes  at  last  to  the  surface  of  the  water.  This  is  possible 
only  through  the  eggs  taking  up  substances  which  have  a 
lower  specific  gravity  than  the  sea-water,  and  the  only  sub- 
stance that  could,  in  this  case,  be  taken  up  is  water.  As  the 
cells  themselves  do  not  become  larger,  we  must  assume  that 
by  a  process  of  secretion  the  segmentation-cavity  is  filled  with 
a  liquid  of  lower  specific  gravity  than  sea-water.  In  this  way 
the  cells  of  the  blastula  come  to  have  their  peripheral  surfaces 
in  contact  with  sea-water  while  their  central  surfaces  are  in 
contact  with  a  fluid  containing  less  salts.  This  might  result 
in  such  differences  of  tension,  between  the  inner  and  outer 
walls  of  the  blastula  as  to  determine  invagination.  I  found, 
last  year,  that  when  I  raised  the  eggs  in  diluted  sea-water, 
evagination  (Fig.  28),  instead  of  invagination,  took  place. 
Herbst  got  the  same  result  by  using  solutions  of  lithium  salts. ^ 
It  is  possible,  too,  that  in  these  cases  the  hydrostatic  pressure 
within  the  segmentation-cavity  is  increased,  and  this  increase 
of  pressure  may  have  a  direct  or  an  indirect  effect  upon 
growth. 

It  is  for  further  investigation,  and  not  for  speculation,  to 
settle  all  these  questions  in  detail.  I  only  wish  to  point  out 
where,  and  how  far,  there  exists  a  relation  between  substance 
and  form  in  the  early  stages  of  the  development  of  the  sea- 
urchin. 

I  have  chosen  the  name  Physiological  Morphology  for  these 
investigations,  inasmuch  as  their  object  has  been  to  derive  the 

1  Herbst,  Zeitschr.  f.  wissensch.  Zool.,  Bd.  55. 


ON  PHYSIOLOGICAL   MORPHOLOGY.  6 1 

laws  of  organization  from  the  common  source  of  all  life  phe- 
nomena, i.  e.,  the  chemical  activity  of  the  cell.  In  what  way 
this  is  to  be  done  is  indicated  in  the  chapter  on  the  mechanics 
of  growth. 

But  the  aim  of  Physiological  Morphology  is  not  alone  an 
analytical  one.  It  has  another  and  higher  aim,  which  is 
synthetical  or  constructive,  that  is,  to  form  new  combina- 
tions from  the  elements  of  living  nature,  just  as  the  physicist 
and  chemist  form  new  combinations  from  the  elements  of 
non-living  nature. 


FOURTH    LECTURE. 

DYNAMICS    IN    EVOLUTION. 

JOHN    A.   RYDER. 

The  statement  that  energy,  in  its  kinetic  and  static  forms, 
has  been  a  factor  in  the  production  of  the  shapes  of  organisms, 
does  not  admit  of  question  at  the  present  time.  In  order  that 
the  data  in  support  of  this  statement  may  be  presented  in  their 
simplest  forms,  it  is  necessary  to  begin  with  the  consideration  of 
the  physical  causes  of  the  configuration  of  some  of  the  simplest 
unicellular  organisms.  In  this  way  it  will  eventually  be  pos- 
sible to  pass  from  the  consideration  of  the  unicellular  to  that 
of  the  multicellular  type,  viewed  from  the  same  standpoint. 
It  requires  but  little  familiarity  with  the  principles  of  physical 
science  to  discover  that  similar  laws  hold  with  respect  to  the 
behavior  of  fluid  and  semi-fluid  bodies,  notwithstanding  the 
fact  that  we  may  have  before  us,  in  one  case,  a  so-called 
"dead"  fluid  body,  and  in  the  other,  a  fluid  ox  fluent  **  living  " 
chemical  compound  or  mixture  of  compounds.  Though  the  one 
presents  the  phenomena  of  'dead,'  and  the  other  of  living, 
matter,  both  exhibit  the  similar  and  common  properties  of 
fluids,  namely,  those  of  surface-tension,  viscosity  and  adhesion 
to  the  surfaces  of  other  bodies,  with  which  they  are  brought 
into  contact.  Under  certain  conditions,  also,  the  semi-fluid 
cells  of  living  bodies  undergo  reciprocal  deformation  or  altera- 
tion in  configuration,  as  a  result  of  the  interaction  of  the 
inherent  forces  above  specified,  in  ways  so  precisely  similar  to 
those  seen  when  a  number  of  semi-fluid,  or  fluid  dead  masses, 
are  juxtaposed  or  brought  into  contact,  that  the  resemblances 
are  seen  to  be  due  to  the  cooperation  of  closely  similar,  if  not 
identical,  forces  and  properties. 


64  BIOLOGICAL   LECTURES. 

This  remarkable  resemblance  of  the  physical  behavior  of 
semi-fluid  living  protoplasm  to  that  of  semi-fluid  dead  matter 
of  certain  kinds,  such  as  the  oils,  has  led  me  to  apply  the  term 
cytophysics  to  the  study  of  the  physical  properties  of  the 
substance  of  the  cell.  The  convenient  terms  cytostatics  and 
cytokinctics  very  naturally  follow  from  a  consideration  of 
the  contrasted  states  of  rest  and  activity  presented  by  the 
^'living"  cellular  unit  of  organization.  The  cytostatic  state 
will  be  one  in  which  no  visible  physical  activity,  other  than 
its  secular  metabolism,  will  characterize  the  cell,  during  which 
time,  also,  the  parts  of  its  substance  will  be  in  a  condition  of 
statical  equilibrium  in  respect  to  each  other,  and  the  cell  will, 
so  long  as  this  equilibrium  lasts,  maintain  a  constant  configu- 
ration. The  cytokinetic  state,  on  the  other  hand,  is  one  in 
which  the  visible  or  invisible  parts  of  the  cell  are  undergoing 
a  displacement  in  respect  to  each  other,  as  a  consequence  of 
which  the  cell  as  a  whole  will  manifest  changes  of  configuration. 

Free  and  interfacial  surface-tension  is  probably  the  most 
important  factor  in  determining  the  shapes  of  cells,  since 
there  is  associated  with  it,  in  multicellular  organisms,  a  com- 
plicated series  of  definite  and  constant  space  relations  and 
reciprocal  interactions,  as  respects  the  cells  of  definite  tissue- 
tracts,  that  grow  out  of  the  very  conditions  of  combination  of 
those  tracts.  Still  more  important,  perhaps,  are  the  incessant 
unequal  disturbances  of  surface-tension,  due  to  metabolic 
changes,  at  different  points  on  the  surfaces  of  cellular  masses 
of  plasma  —  a  fact  beautifully  illustrated  by  the  proteus  ani- 
malcule, Amoeba  pivtens.  Differences  of  surface-tension  are 
thus  developed  at  different  points  and  times  coexistently  and 
consecutively  which  lead  to  the  assumption  of  the  most  diverse 
and  inconstant  shapes  by  the  bodies  of  these  lowly  organisms. 
Such  differences  of  surface-tension  are,  however,  themselves 
caused  by  chemical  and  molecular  transformations  at  definite, 
but  previously  unspecifiable,  points  at  or  near  the  surface  of 
the  mass  of  plasma.  These  processes  are,  therefore,  ultimately 
to  be  associated  with  molecular  or  chemical  transformations, 
the  production  of  heat,  the  disintegration  and  integration  of 
living  matter. 


DYNAMICS  IN  EVOLUTION.  65 

But,  it  will  be  asked,  what  is  surface-tension  ?  If  a  drop  of 
water  falls  through  a  vacuum,  as  long  as  it  is  falling  in  space 
it  will  present  very  nearly  the  form  of  a  sphere.  This  is  due 
to  the  fact  that  the  very  outermost  layers  of  molecules  which 
lie  at  insensible  distances  apart,  attract  each  other  with  a  force 
that  is  apparently  very  much  greater  than  that  developed  by 
the  action  of  gravitation.  It  results  from  this  that  the  remain- 
ing molecules  contained  within  this  outer  molecular  film  are 
held  as  within  an  elastic  bag,  the  walls  of  which  are  of  exactly 
the  same  strength  at  every  point.  This  exactly  equal  strength 
and  elasticity  of  the  outer  molecular  film  at  every  point  on  the 
surface  also  causes  it  to  fall  into  a  condition  of  spherical^ 
statical  equilibrium.  This  is  true  because  the  molecules  at 
every  point  on  the  surface  of  the  drop  are  of  exactly  the  same 
size,  therefore  every  one  attracts  its  fellows  that  are  in  contact 
with  it,  with  exactly  the  same  force  at  every  point  on  that 
surface.  Now,  let  any  change  in  the  dimensions  of  these 
molecules  occur  at  any  point  on  the  surface  of  such  a  fluid 
sphere,  such  as  may  be  accomplished  by  chemical  transforma- 
tions and  recombinations,  such  as  oxidation  or  decomposition, 
and  it  must  follow  that  the  surface-tension  or  reciprocal  pull 
of  the  molecules  upon  each  other,  adjacent  to  the  point  of 
such  disturbance,  must  be  increased  or  diminished.  The 
inevitable  result  of  this  will  be  that  the  form  of  the  drop  must 
instantly  change  in  order  that  a  new  condition  of  statical 
equilibrium  may  be  attained.  The  surface  of  the  drop  is 
finite  and  returns  in  every  direction  upon  itself  since  it  is 
approximately  spherical.  Any  deformation  of  the  drop  due  to 
surface-tensional  disturbances  will  therefore  affect  the  shape  and 
curvature  of  some  or  all  of  the  surface  of  the  drop  so  that  its 
shape  may  become  very  irregular,  provided  its  surface-tension 
be  disturbed  at  a  number  of  irregularly  distributed  points 
simultaneously  ;  but,  since  the  drop  is  a  finite  mass  made  up 
of  solid  particles  moving  freely  among  themselves,  no  matter 
how  much  the  drop  may  be  deformed  or  how  irregular  it  may 
become,  its  most  superficial  layer  of  molecules  will  always  form 
a  closed  surface.  This  fact  is  important,  since,  no  matter  how 
irregular  in  shape  an  Amoeba  may  become,  its  outermost  stratum 


66  BIOLOGICAL   LECTURES. 

of  molecules  always  form  a  closed  surface  and  a  molecular 
envelope  for  the  organism. 

Since  the  molecules  within  a  semi-fluid  mass  also  move  freely 
over  one  another  there  is  friction  developed  between  them. 
This  friction  is  known  as  viscosity,  and  differs  in  fluids  of 
differing  densities  and  chemical  compositions,  just  as,  in  fact, 
the  surface-tension  of  a  unit- surface,  formed  of  different  fluids, 
differs,  owing  to  the  differing  dimensions  and  properties  of  the 
superficial  layer  of  molecules  of  each  fluid.  The  specific 
viscosities  and  surface-tensions  manifested  by  any  given  fluid 
are  therefore  correlated,  so  that  we  may  infer  that  these  two 
properties  of  fluent  living  matter  are  also  correlated.  Since, 
again,  living  matter,  as  found  in  the  cell,  is  not  a  homogeneous 
body  or  compound,  it  will  be  plain  that  the  correlative  disturb- 
ances in  viscosity  and  surface-tension,  due  to  the  processes  of 
metabolism  and  the  associated  interplay  of  osmotic  changes, 
are  so  complex,  when  considered  together  with  still  other  facts, 
that  it  will  be  difficult,  if  not  impossible,  in  the  present  state 
of  our  knowledge,  to  trace  all  the  steps  of  their  interrelations 
and  interdependences  in  any  given  case. 

The  recent  progress  in  the  study  of  the  process  of  fertiliza- 
tion or  conjugation  shows  that  dynamical  considerations  must 
here  also  be  taken  into  account.  As  is  well  known,  the  nucleus 
and  archoplasm  undergo  alternate  expansion  and  contraction 
in  linear  dimensions.  The  male  and  female  pronuclei  increase 
greatly  in  size  during  the  phases  just  before  conjugation.  In  the 
^'g^  oi  Ascaris,  for  example,  I  have  noticed  that  the  pronuclei 
soon  assume  a  globular  form  and  rapidly  grow  into  large 
spherical  bodies  by  absorbing  substance  from  the  surrounding 
cytoplasm.  This  rapid  growth  and  spherical  form  show  that 
surface-tension  is  being  disturbed  uniformly  over  the  whole 
surface  of  the  nucleus,  otherwise  its  form  could  not  re^nain 
spherical.  The  remarkable  growth  of  the  rays  of  the  asters 
has  the  same  meaning  and  must  also  be  interpreted,  in  part,  as 
a  physical  process  involving  radial  interdiffusion  of  heteroge- 
neous molecules  to  and  from  the  centrosomes  into  the  nucleus 
and  cytoplasm,  consequent  osmotic  disturbances,  metabolism 
and  changes  of  surface-tension.     The  comparison  of  the  astral 


DYNAMICS  IN  EVOLUTION.  67 

figures,  with  their  rays  extending  in  every  direction  from  the 
archoplasm,  with  the  rays  developed  on  the  surface  of  a  fluid 
when  another  fluid  of  definite  properties  is  dropped  upon  the 
former,  leading  instantly  to  the  production  of  a  "  cohesion 
figure"  with  rays  extending  out  in  every  direction,  is  no  mere 
analogy.  In  the  case  of  the  archoplasm,  the  rays  with  their 
lines  of  microsomes  are  probably  the  effects  of  diffusion  of 
one  kind  of  plasma,  the  archoplasm,  through  another,  the 
cytoplasm,  and  is  therefore  not  necessarily  a  phenomenon  of 
contractility,  but  simply  an  interdiffusion  of  the  unlike  sub- 
stances produced  by  the  metabolism  of  growth,  which  tends  to 
reestablish  statical  equilibrium  among  the  parts  of  the  molecular 
system  represented  by  the  cell.  This  diffusion  or  osmotic 
redistribution  is  conditioned  at  every  step  by  surface-tension  in 
precisely  the  same  way  that  the  rays  of  many  Heliozoa  and 
Radiolarians  are  conditioned  in  water  by  states  of  unequal 
surface-tension  at  very  close  but  nearly  equal  intervals  over  a 
spherical  surface,  so  that  a  summation  of  these  uniformly 
distributed  and  seemingly  conflicting  surface  tensional  forces 
does  not  interfere  with  the  maintenance  of  the  spherical  figure 
by  the  body  of  the  organism.  The  alternate  inflation  and  col- 
lapse of  the  nucleus  during  fertilization,  and  growth  during 
indirect  cell-division,  is  a  rhythmical  process,  and  we  may  char- 
acterize it  as  the  diastole  and  systole  of  the  nucleus.  The  alter- 
nate extension  and  retraction  of  the  rays  of  the  archoplasm,  as 
I  have  observed  in  the  Q.^g  of  Ascaris,  is  similarly  an  osmotic  or 
metabolic  diastole  and  systole  of  the  radial  figures  formed  by  it, 
which  is  intimately  associated  with  and  absolutely  conditioned 
by  metabolism  and  osmosis,  as  the  direct  experimental  researches 
of  Prof.  Jacques  Loeb  have  rendered  exceedingly  probable. 
Unless  the  processes  of  karyokinesis  are  traced  with  the 
utmost  caution  in  the  light  of  dynamical  and  physiological 
considerations,  there  is  great  danger  of  our  misinterpreting  the 
facts  and  of  assuming  that  certain  of  the  phenomena  guide 
and  control  others.  It  may  indeed  be  possible  that  embryolo- 
gists  have  been  until  now  steadily  confounding  ontogenetic 
effects  due  to  the  physical  processes  of  growth,  as  visualized 
in    karyokinesis,   with    their    causes.      I    anticipate    that    this 


68  BIOLOGICAL   LECTURES. 

remark  will  meet  with  a  decided  denial  from  most  morpholo- 
gists  ;  nevertheless  it  seems  opportune  to  warn  them  that  the 
problems  they  have  before  them  can  never  be  settled  by  purely 
morphological  methods.  If  my  contention  that  all  ontogenetic 
problems  must  be  approached  by  a  most  intimate  combination 
of  the  methods  of  physical,  physiological  and  morphological 
research  is  true,  we  are  still  far  from  having  anywhere  an 
ideal  biological  investigator.  If  it  is  true  that  "we  have  been 
mistaking  ontogenetic  effects  for  ontogenetic  causes,  what  a 
mass  of  speculation  must  probably  be  set  aside.  All  that  will 
remain,  in  fact,  will  be  the  many  most  valuable  and  beautiful 
results  of  observation  made  by  our  foremost  morphologists. 

It  is  not  intended  to  thus  minimize  in  any  way  the  great 
and  increasing  value  of  morphological  research  ;  what  is  really 
meant  is,  that  there  is  danger  of  overrating  the  importance  of 
morphology  to  the  injury  or  exclusion  of  other  disciplines  of 
paramount  importance.  If,  as  we  must  suppose,  there  is  such 
a  perpetual  flux  and  interflux  of  particles  and  molecules  going 
on  throughout  the  plasma  of  an  ^g^,  owing  to  the  metabolism 
due  to  respiration  and  the  consequent  surface-tensional  and 
osmotic  disturbances  during  the  earliest  steps  of  development, 
it  becomes  inconceivable  that  any  such  morphologically  con- 
ceived and  entirely  hypothetical  bodies  as  *Mds,"  "idants," 
"determinates,"  etc.,  can  have  a  stable  existence.  The  exist- 
ence of  such  bodies  as  fixed  entities  of  finite  complexity  is 
absolutely  disproved  by  experiments  of  the  most  varied  charac- 
ter in  separating  the  first  two  or  four  blastomeres  of  the  ^gg, 
since  it  is  then  found  that,  in  each  of  these  blastomeres,  there 
still  inheres  the  power  to  produce  a  perfect  embryo.  The 
hypothetical  ids,  determinants,  biophores,  gemimiles,  etc.,  must, 
therefore,  be  supposed  to  be  capable  of  being  halved  and  then 
quartered  without  destroying  their  potentialities.  These  and 
numerous  other  difficulties  that  cannot  be  discussed  here, 
render  it  exceedingly  probable  that  we  must  look  in  altogether 
another  direction  for  an  explanation  of  the  processes  of 
ontogeny,  viz.,  to  a  study  of  the  modes  and  conditions  of  the 
manifestations  of  the  energies  that  constitute  the  'Mife"  of 
the   simplest   organized  forms. 


DYNAMICS  IN  EVOLUTION.  69 

In  the  very  simplest  unicellular  organisms  we  have  also 
unicellular  molecular  mechanisms  of  a  most  peculiar  kind. 
The  fearfully  complex  molecular  structure  of  these  mechan- 
isms conditions  their  actions,  their  forms  and  powers,  no  less 
than  does  the  nature  of  the  watery  media,  in  which  these  first- 
lings of  life,  as  well  as  the  germs  of  higher  organisms,  must 
in  common  develop.  In  the  belief  that  the  study  of  the 
''living"  mechanism  of  some  of  the  lowest  types  of  organized 
existence,  in  relation  to  and  as  affected  by  their  not-living  sur- 
roundings, might  throw  some  light  upon  the  origin  of  their 
forms,  the  writer  has  here,  in  the  main,  taken  up  the  problems 
thus  raised  as  physical  ones.  In  the  belief,  also,  that  these 
studies  have  not  been  entirely  fruitless,  the  following  evidence 
is  offered. 

An  Amoeba  proieits  may  be  compared  to  a  smoke-  or  vortex- 
ring  of  particles  that  has  been  greatly  modified,  owing  to  the 
very  complex  interaction  of  disturbances  of  the  surface-tension 
of  its  outer  enveloping  film  of  molecules,  the  viscosity  of  its 
own  plasma,  its  gravity  and  power  of  adhesion  to  other  bodies. 
If  we  conceive  a  smoke-ring  to  have  become  a  viscous  semi- 
fluid body  with  an  outer  film  of  molecules,  and  that  this  ring 
has  contracted  until  the  central  opening  in  it  has  completely 
closed,  we  shall  have  a  mechanism  which  may  be  compared  in 
detail  with  an  Amoeba  in  motion,  provided  only  that  we  modify 
it  still  further  and  in  such  ways  as  we  are  obliged  to  suppose 
that  the  combination  of  the  four  forces  above  specified  cooper- 
ate in  order  to  produce  and  maintain  the  form  of  an  amoeboid 
organism.  Verworn^  has  already  referred  to  the  flux  of  the 
particles  of  the  Amoeba  through  itself,  in  discussing  the 
general  subject  of  contraction,  but  as  he  has  not  understood 
the  complexity  of  the  process,  we  need  not  here  concern 
ourselves  further  than  to  say  that  he  has  failed  to  correctly 
interpret  this  vortical  flux  of  amoeboid  organisms.  There 
is,  however,  such  a  central  flux  of  particles  through  the  centre 
of  the  body  of  an  amoeboid,  as  any  one  can  soon  convince 
himself  by  carefully  observing  the  behavior  of  a  large  living 
proteus  animalcule.      The  chemical  transformations  that  go  on 

1  Bewegung  der  lebendigen  Substanz.     Jena,  1892. 


70 


BIOLOGICAL   LECTURES. 


within  the  body  of  an  amoeboid,  amongst  its  molecules,  are 
responsible  for  disturbances  of  the  surface-tension  at  one  or 
more  points  over  its  surface.  It  is  certain  that  the  chemo- 
tropism,  or  affinity  for  oxygen  of  its  surface  molecules,  as  Ver- 
worn  holds,  is  essential  to  this;  but  we  must  remember  that  in 
order  to  call  forth  local  disturbances  of  surface-tension  in  this 
way,  there  must  also  be  a  locally  exaggerated  chemotropism,  or 
affinity  for  oxygen,  at  some  one  point  on  the  surface  of  the 
organism.  This  point  has  apparently  not  been  made  clear  by 
Verworn,  but  it  is  essential  to  a  clear  understanding  of  the 
processes  presently  to  be  described.  How  the  positions  of 
such  local  disturbances  of  the  chemical  complexity  of  the  sur- 
face-layer of  molecules  of  an  amoeboid  arc  determined,  we  do 
not  know.  That  they  are  definitely  determined,  according  to 
some  definite  law,  we  may  be  certain. 

As  every  one  knows  who  has  ever  watched  a  proteus  animal- 
cule under  the  microscope,  the  "anterior"  pole  of  the  creature, 
for  the  time  being,  is  tensely  filled  with  its  own  substance,  so 
as  to  present  a  rounded,  full  ''anterior"  extremity  while  in 
motion.  ''Posteriorly,"  on  the  other  hand,  the  creature  is 
found  to  present  a  wrinkled,  partially  collapsed  appearance. 
A  study  of  the  motions  of  the  organism  discloses  the  fact  that 
its  substance  is  flowing  through  itself.  The  central  part  of 
this  current  is  moving  most  rapidly  along  the  middle  of  the 
body,  while  toward  the  sides  it  is  observed  to  become  progress- 
ively slower  until  the  outer  layers  of  its  substance,  along  the 
sides  of  the  creature,  are  seen  to  come  to  rest.  It  thus  results 
that  the  outer  layers  of  molecules,  along  the  sides,  form  a  sort 
of  shell  or  tunnel  through  which  the  central  current  flows. 
This  flux,  however,  means  that  there  must  be  a  continual  or 
fitful  rupture  of  the  "anterior"  end  of  the  organism  in  order 
to  let  some  of  itself  escape  out  of  itself  in  front,  in  order  to  let 
some  of  itself  flow  into  itself  behind,  in  order  that  some  of 
itself  may  thus  continuously  flow  through  itself  in  order  to 
make  the  progressive  forward  motion  of  itself  possible.  In 
this  way  the  substance  of  the  "posterior"  part  of  the  organism 
can  be  picked  up  and  carried  through  the  tunnel-like  physical 
shell,  formed  of  the  outer  layers  of  molecules  of  the  organism, 


DYNAMICS  IN  EVOLUTION.  71 

and  thus  be  transported  forwards  and  poured  out  ''anteriorly." 
It  will  readily  be  seen  that,  in  order  to  do  this,  work  must  be 
performed,  energy  dissipated.  This  energy  is  dissipated  in 
reestablishing  a  dynamical  balance  between  the  parts  of  the  dy- 
namical system  represented  by  the  molecular  aggregate  that  we 
behold  in  the  body  of  the  Amoeba.  We  have  here  before  us  a 
finite  molecular  mechanism,  or  dynamical  system,  every  part  of 
the  surface  of  which  returns  upon  itself.  Any  disturbance  of 
the  equilibrium  of  the  molecules  at  the  surface  of  that  system 
will  provoke  a  deformation  of  the  whole.  If  the  disturbance 
is  great  enough  at  any  one  point,  there  will  inevitably  be 
developed  a  vortex-ring  motion  of  the  particles  amongst  them- 
selves, due  to  the  friction  of  the  constituent  molecules.  If 
this  vortical  motion  of  the  particles  of  an  amoeboid  mass  of 
** living"  matter  be  due  to  a  preponderating  superficial  dis- 
turbance of  the  equilibrium  of  the  system  at  one  point  on  the 
surface,  that  alone  will  suffice  to  determine  the  direction  of 
the  motion  of  the  whole.  For  this  reason  the  proteus  animal- 
cule has  no  fixed  ''head"  or  "tail"  end.  "Head"  and  "tail" 
seems  to  be  entirely  a  matter  of  the  combination  of  inner  and 
outer  conditions  that  determine  the  point  on  the  surface  of  the 
organism,  at  which  the  maximum  chemical  and  physical  dis- 
turbance of  surface-tension  will  occur.  These  are  absolutely 
determined  by  the  physical  processes  of  the  readjustment  of 
the  equilibrium  of  its  molecules,  in  respect  to  outer  conditions, 
during  every  consecutive  moment  of  its  motions.  It  is  pos- 
sible, in  fact,  to  show  that  every  change  of  the  shape  of  this 
interesting  organism  is  the  result  of  energies  inter-acting  in  a 
very  complex  way. 

If  an  Amoeba  is  allowed  to  fall  through  the  water,  its 
surface-tensions  are  apparently  disturbed  with  great  uniformity 
over  its  whole  surface,  and  at  nearly  equal  distances  apart. 
It  results  from  this  that  short,  blunt  pseudopodia  are  pushed 
out  in  every  direction,  as  in  Fig.  i  and  it  becomes  nearly 
globular  in  outline.  The  moment,  however,  that  the  organ- 
ism touches  a  plane  surface,  as  in  Fig.  2,  it  flattens  out 
into  the  form  of  a  biscuit-shaped  mass.  It  now  behaves 
like    a    mass    of    dough,    and    falls    into    a    new    condition    of 


72 


BIOLOGICAL   LECTURES. 


equilibrium,  due  to  its  own  gravity,  its  viscosity,  and  the 
force  with  which  the  particles  on  its  under  side  tend  to  adhere 
to  the  fixed  solid  surface  upon  which  it  rests.  The  upper  part 
of  the  mass  now  falls  into  an  equilibrium  determined  by  the 
surface-tension  of  its  superficial  molecules  and  the  viscosity  or 
reciprocal  friction  of  the  latter  upon  each  other.  Gravity, 
viscosity,  surface-tension,  and  adhesion  are  the  four  cooper- 
ating agents  that  now  determine  its  figure.  So  long  as  it  was 
floating  or  suspended  in  the  water,  the  influence  of  gravity 
and  adhesion  operating  in  relation  to  a  fixed  surface  were 
excluded.  We  thus  see  how  completely  this  organism  is 
the  creature  or  subject  of  energy-conditions  in  this  state. 


In  the  next  phase  of  its  motions  this  is  still  further 
illustrated.  In  Figs,  i  and  2,  short,  blunt  pseudopodia  are 
being  protruded  in  all  directions;  but  in  Fig.  3,  the  sequence 
of  events  changes,  and  the  organism  begins  to  take  up  its 
march  by  means  of  a  vortical  flux  of  its  substance  across  the 
surface  upon  which  it  rests,  and  in  the  direction  of  the  arrow. 
Surface-tensional  disturbances  of  greater  magnitude  have  evi- 
dently affected  the  right  side  of  the  mass,  and  one  or  more  of 
the  small  original  blunt  pseudopodia  at  this  point  have  been 
merged  into  a  strong,  single  ''anterior,"  pseudopodal  current, 
in  which  a  maximum  flux  of  molecules  is  taking  place  in  the 


DYNAMICS  IN  EVOLUTION,  73 

direction  of  the  motion  of  the  whole  organism.  This  maximum 
vortical  flux  of  the  material  particles  of  the  amoeboid  in  this 
new  direction  will  result  in  elongating  the  organism  in  th 
direction  of  the  motion  thus  set  up.  The  elongation  of  the 
organism  is,  therefore,  due  to  the  flow  of  its  own  particles 
amongst  and  through  themselves.  We  are  thus  made  aware 
of  the  fact  that  this  simplest  organism  is  elongated  in  the 
direction  of  its  own  motions,  as  a  consequence  of  the  continuous 
readjustment  of  the  internal  equilibrium  of  its  parts  in  respect 
to  influences  affecting  it  from  without.  The  shape  of  this 
organism,  at  every  instant  of  its  motions,  is,  therefore, 
mechanically  caused. 

We  may  pursue  our  analyses  still  further.  If  we  now  look 
down  upon  such  an  amoeboid  organism  from  above,  when 
moving  upon  a  plane  surface,  as  in  Fig.  4,  we  find  that  it  is 
not  only  elongated  in  the  direction  of  its  motion,  but  that  its 
anterior  end  is  tensely  filled  with  substance;  its  outer  layer  of 
molecules  at  the  "anterior"  end  is  tensely  stretched.  At  the 
tail  end  the  organism  is  wrinkled  or  papillated;  this  wrinkled 
or  papillated  appearance  of  the  posterior  end  of  the  organism 
is  due  to  physical  causes,  as  the  following  observation  proves: 
In  Fig.  4  there  are  two  anterior  pseudopodia,  —  b  and  c,  — 
through  which  there  are  fluxes  of  particles  in  progress  at 
about  the  same  rate.  The  vortical  current  is  seen  to  divide 
and  to  flow  into  both  these  pseudopodia,  thus  keeping  the 
outer  molecular  film  over  both  tense  and  rounded.  Let, 
however,  a  disturbance  of  the  surface-tension  occur  at  the 
end  of  b,  while  at  the  end  of  c^  this  disturbance  subsides,  as 
in  Fig.  5  and  there  will  be  a  flux  of  particles  out  of  r'  —  in 
the  direction  of  the  arrow — into  /;,  and  r'  will  lose  its  tense, 
full  outline,  and  its  surface  will  become  wrinkled  or  papillated, 
just  as  appears  at  the  "tail"  end  of  the  organism  at  a.  In 
every  detail  of  the  morphology  of  this  organism,  we  therefore 
discover  that  physical  or  "  physiological "  agencies  are 
operative  in  determining  its  figure.  We  are,  therefore,  in  a 
position  to  afiirm,  with  positive  certainty,  that  the  morphology 
of  this  organism  has  little  significance  until  its  actions  and 
their  physical  causes  have  been  studied.      This  is  only  one  of 


74  BIOLOGICAL   LECTURES. 

many  reasons  why  the  present  speaker  holds  that  all  purely 
morphological  work  is  one-sided,  and  incapable  of  dealing  with 
the  deeper  problems  of  biology.  In  the  same  way,  physiology 
alone  is  equally  incapable  of  dealing  with  the  great  general 
problems  in  biology.  Neither  of  the  two  disciplines  alone  can 
ever,  by  any  stretch  of  imagination,  command  the  power  to 
produce  a  theory  of  life.  Such  an  expectation  is  simply 
fatuous. 

The  many  other  dynamical  phenomena,  especially  the  singular 
manner  in  which  the  nucleus  of  an  Amoeba  proteiis  is  caused 
to  oscillate  back  and  forth  within  its  body  within  certain  limits, 
all  take  place  in  accord  with  the  views  above  developed.  For 
example,  the  curious  lateral  flow  of  the  plasma  of  Ama;ba proieiis 
when  in  a  fully  extended  condition,  along  the  sides  of  the 
body  on  either  side  of  its  posterior  and  middle  thirds,  may  be 
explained  by  the  physical  tendency  of  this  part  of  the  organism 
to  adhere  to  the  substratum  upon  which  it  is  moving.  This 
lateral  spreading  does  not  take  place  at  its  *'  anterior  "  end 
because  here  the  influx  of  molecules  from  behind  is  taking 
place  so  rapidly  that  this  spreading  due  to  adhesion  has  not 
yet  had  time  to  take  place.  This  spreading  due  to  adhesion 
causes  the  central  current  to  be  narrowed  and  elevated  so  that 
the  discoidal  nucleus  is  lifted  and  rolled  along  on  its  edge  in 
this  narrow  elevated  part  of  the  body  of  the  organism  as  if 
passing  through  a  tunnel  with  its  sides  wider  than  its  floor. 
Rolled  along  in  this  way  through  this  narrow  passage  by  the 
vortical  current  of  plasma,  the  nucleus  is  finally  arrested  by 
contact  of  its  edge  with  the  molecular  boundary  wall  of  the 
organism,  and  is  thus  automatically  kept  from  being  bodily 
rolled  to  the  outside  of  the  plasma  of  the  organism.  Reaching 
a  certain  point  at  the  ''anterior"  end  of  the  mass  of  plasma, 
it  also  falls  over  on  its  side,  wedged  between  the  roof  and  floor 
of  the  mass  of  plasma  of  which  it  forms  a  part.  It  is  thus 
prevented  from  passing  out  of  the  organism  with  the  vortical 
current  that  must  now  flow  past  it  and  on  forward  to  continually 
form  anew  the  ''anterior"  end  of  this  singular  being  that  is 
thus  continually  turning  itself  inside  outward  in  front  and 
outside  inward  behind. 


DYNAMICS  IN  EVOLUTION.  75 

The  manner  in  which  the  successive  rents  in  the  outer 
molecular  skin  of  the  organism  are  produced  is  such  that  a 
sudden  rupture  occurs  through  which  a  fresh  outpour  of 
substance  happens  over  which  a  new  molecular  skin  is  instantly 
formed  continuous  with  the  ruptured  edge  of  the  old.  These 
rents  do  not  take  place  in  relatively  the  same  place  in  succession. 
For  example,  rents  may  occur  in  the  outer  film  one  after  the 
other  at  points  a  little  off  of  the  extreme  central  point  of  the 
''  anterior  '*  end,  and  alternately  a  little  to  the  right  and  left  side 
of  the  latter.  The  vortical  flux  is  thus  thrown  slightly  aside 
alternately  to  the  right  and  then  to  the  left,  then  to  the  right, 
then  to  the  left  again,  and  so  on,  indefinitely.  It  thus  results, 
however,  that  the  summation  of  these  alternating  outbursts  of 
substance  become  the  components  of  the  aggregate  motion  of 
the  whole  organism  in  one  general  direction. 

If  a  rent  occurs  at  one  side  of  the  organism,  due  to  a 
disturbance  of  surface-tension  at  an  anterior  lateral  point,  a 
lateral  flux  of  particles  may  thus  be  set  up,  as  a  result  of 
which  the  entire  contents  of  the  organism  may  be  sucked  up 
''anteriorly"  and  ''posteriorly"  to  the  point  where  the  new 
outflow  has  taken  place.  In  other  words,  the  "head"  and 
"  tail "  ends  of  the  organism  may  be  thus  caused  to  flow  in 
opposite  directions  into  the  lateral  outburst  and  the  whole 
organism  take  a  new  direction  of  motion  with  all  its  parts 
oriented  in  respect  thereto.  Amceba  protciis,  therefore,  cannot 
move  except  by  developing  a  vortical  flux  of  particles,  and 
it  therefore  is  a  "living"  vortex-ring  of  particles.  These 
outbursts,  in  large  individuals,  occur  successively  at  short 
intervals  of  time,  so  that  the  motion  of  the  creature  is 
fitful.  In  young  protcus  animalcules  the  bursting  out  or 
pouring  forth  of  the  plasma  at  the  "anterior"  end  maybe 
continuous,  so  that  the  motion  is  uniform  and  an  ideally  perfect 
type  of  the  "living"  vortex-ring  of  particles  is  realized. 

Every  pseudopodium  is,  however,  so  long  as  it  is  being 
protruded,  a  vortex-current  in  which  the  motion  of  the  particles 
is  swiftest  at  its  center  and  at  its  tip,  while  at  the  sides  the 
particles  are  quiescent  and  form  a  shell  through  which  the 
central  ones  are  moving.     The  pseudopodia,  therefore,  divide 


76  BIOLOGICAL   LECTURES. 

the  vortex-current  of  particles  into  diverging  currents,  the 
summation  of  the  motions  of  which  may,  when  the  organism 
is  moving  on  a  plane  surface,  become  resolved  mechanically 
into  a  single  motion  of  translation  in  one  direction. 

When  the  organism  is  freely  suspended  in  water  it  protrudes 
pseudopodia  equally  in  every  direction  and  assumes  a  globular 
figure,  somewhat  like  a  Heliozoan  or  Radiolarian,  because 
its  surface-tension  is  now  being  disturbed  at  nearly  equally 
separated  points  over  its  whole  surface.  It  therefore  falls  into 
a  condition  of  spherical  equilibrium,  since  the  components  of 
all  the  surface-tensions  are  resolved  at  the  centre  of  the 
organism.  The  moment  it  touches  a  fixed  surface,  distortion  of 
the  formerly  globular  organism  takes  place  under  the  influence 
of  gravity  and  adhesion,  and  the  vortical  flux  of  particles  that 
is  now  set  up  is  different  in  nature  from  that  which  took  place 
in  every  direction  when  it  was  in  the  suspended  globular  con- 
dition. There  is  at  once  a  maximum  flux  of  particles  in  the 
direction  of  the  point  at  which  the  most  active  disturbance  of 
surface-tension  occurred,  and  the  resulting  current  becomes  very 
massive  so  that  the  whole  contents  of  the  organism,  except  the 
nucleus  and  water  vacuole,  flow  forward  as  a  massive  pseudopod, 
that  is  somewhat  flattened  or  depressed  by  the  action  of  gravity 
and  adhesion,  but  which  is  much  larger  than  any  of  those 
produced  while  in  the  spherical  condition.  How  little  Verworn 
has  appreciated  and  understood  these  complex  processes  may 
be  judged  by  any  one  who  has  read  his  work  on  the  motion  of 
living  substance.  He  has  affirmed  what  does  not  exist  in 
regard  to  small  Amoeba  proteus,  where  the  flux  is  continuous 
and  where  no  retreat  of  particles  to  the  nucleus,  such  as  he 
postulates,  can  take  place  for  hours  together.  In  short, 
Verworn  has  totally  failed  to  understand  the  real  significance 
of  these  complex  phenomena.  Greef,  also,  has  made  assump- 
tions with  regard  to  amoeboid  motion,  especially  the  existence 
of  muscular  fibrils,  which  by  no  stretch  of  the  imagination  can 
be  conceived  to  hold  of  the  proteus  animalcule. 

Verworn  has  also  failed  to  understand  the  physical  reasons 
why  small  blebs  or  pseudopodial  warts  were  produced  along  the 
sides  of  a  retracting  pseudopod.     He  speaks  of  "  stimulation  " 


DYNAMICS  IN  EVOLUTION  J  J 

{Reiz),  a  word  which  to  me  has  a  very  indefinite  meaning. 
The  production  of  these  blebs  or  incipient  pseudopodia,  which 
I  have  often  observed,  and  in  a  great  variety  of  forms,  may  be 
equally  well  explained  by  surface-tensional  disturbance,  the 
viscosity  of  the  plasma,  etc.,  and  not  necessarily  as  caused  by 
a  retreat  of  the  substance  toward  the  nucleus,  as  claimed 
by  Verworn,  in  order  to  receive  a  reinforcement  or  accession 
of  new  nuclear  molecules. 

The  differentiation  of  the  substance  of  an  amoeboid,  such  as 
A.  protcus,  into  an  outer  hyaline  layer  and  a  central  or  medul- 
lary part,  —  the  so-called  *'endosarc"  and  ''ectosarc,"  —  is 
again  a  purely  physical  phenomenon.  The  surface-tensional 
forces  rniLst  be  exerted,  for  physical  reasons,  between  molecules 
of  approximately  the  same  dimensions,  otherwise  there  could 
be  no  tolerably  coherent  and  stable  outer  stratum  formed. 
In  other  words,  the  molecules  of  the  outer  layers  are  recipro- 
cally attracted  to  each  other  with  a  greater  force  at  insensible 
distances  apart,  than  the  larger  and  coarser  particles  are 
attracted  by  the  small  uniform  molecules  at  the  same  intervals 
apart.  The  materials  of  an  amoeboid  are  thus  dynamically 
sorted  into  two  kinds,  in  virtue  of  their  differences  of  attrac- 
tion for  one  another.  It  thus  comes  about  that  ''endosarc" 
and  "ectosarc"  are  merely  names  for  the  results  of  a 
dynamical  process  that,  so  to  speak,  sorts  the  particles  of 
a  living  amoeboid  into  two  kinds.  The  small  surface-particles 
or  molecules  necessarily  attract  each  other  under  such  condi- 
tions of  dynamical  advantage  over  and  above  their  attraction 
for  the  larger  particles,  that  the  latter  are  constantly  driven 
inward  and  kept  there  for  this  reason. ^  In  this  case,  again,  a 
morphological  fact  is  only  understood  when  subjected  to 
dynamical   analysis. 

In  this  way  one  might  go  on  and  subject  every  detail  of  the 
organization  of  an  amoeboid  to  physical  scrutiny,  and  show 
that  complex  energy-combinations  determined  every  detail  of 
its  structure.  Not  a  single  amoeboid  form  that  I  have 
yet  encountered  has  failed  to  disclose  this  mechanical 
and  dynamical  complex  of  agencies  as  factors  competent   to 

^  A  geometrical  diagram  would  be  nee:!ed  to  make  this  statement  perfectly  clear. 


yS  BIOLOGICAL  LECTURES. 

determine  its  figure  at  every  instant  of  its  existence.  There 
may  be  those,  however,  who  will  find  fault  with  my  identifi- 
cation of  the  motions  of  an  amoeboid  with  that  of  a  whirl-  or 
vortex-ring  of  particles.  It  may  be  well,  also,  to  explain  here 
that  this  notion  has  nothing  to  do  with  the  physical  con- 
ception of  Lord  Kelvin  respecting  the  existence  of  vortex 
atoms.  The  identification  of  amoeboid  motion  with  a  vortex- 
ring  of  particles  is  perfect,  provided  certain  reservations  are 
made  that  grow  out  of  the  very  nature  of  the  conditions  and 
nature  of  amoeboid  motion.  In  a  typical  smoke-  or  vortex- 
ring  the  impulse  of  rotation  that  impels  all  its  particles  is 
imparted  from  without;  in  the  living  vortex-ring  secular 
changes  in  the  nature  of  its  constituent  particles  condition 
its  motions  and  provoke  them.  And,  while  it  is  true  that  the 
energy  that  drives  the  living  vortex-ring  is  primarily  derived 
from  without,  it  is  not  set  free  until  the  constituent  particles 
have  changed  their  dimensions,  affinities,  and  reciprocal  attrac- 
tions within  the  ring,  due  to  causes  acting  antecedently  from 
without.  The  living  vortex-ring  is  a  constantly  changing, 
closed,  and  regenerative  dynamical  system;  the  other  is  a 
dynamical  system  that  derives  all  its  energy  from  without  in 
the  form  of  a  single  impulse,  and  comes  to  rest  after  a  time, 
owing  to  the  friction  of  its  superficial  particles  with  their 
surroundings. 

It  may  be  objected,  also,  that  there  is  only  a  remote  resem- 
blance of  a  smoke-ring  to  that  of  the  flux  of  living  particles 
through  an  amoeboid  organism.  This  objection  may  be  met 
by  the  statement,  that  not  only  do  I  suppose  the  living  vortex- 
ring  to  be  flattened  by  its  gravity,  but  I  also  suppose  it  to 
have  no  central  opening,  and  that  the  median  longitudinal 
stream  of  particles  represents  the  point  where  the  opening 
would  be  in  a  smoke-ring  —  now  a  line  in  Amoeba — along 
which  the  central  "living"  vortex  current  is  flowing.  I 
moreover  suppose  that  the  ring  is  greatly  elongated,  owing 
to  the  viscosity  of  its  substance  and  the  adhesion  of  the 
surface  of  the  living  amoeboid  to  the  substratum  upon  which 
it  moves.  I  would  not  have  any  one  suppose  that  I  imagined 
that  amoeboids  ever  existed  that  had  a  central  opening  in  them 


DYNAMICS  IN  EVOLUTION.  79 

like  a  smoke-ring.  I  have  only  used  this  comparison  because 
of  the  obvious  identity  of  the  living  and  dead  vortices,  when 
proper  allowance  is  made  for  the  physical  conditions  under 
which  both  subsist  on  account  of  the  different  nature  of  their 
constituent  substances.  The  outer  molecular  shell,  for  example, 
of  a  living  vortex-ring  is  fixed  to  its  substratum,  and  is  only 
involuted  ''posteriorly,"  and  evoluted  ''anteriorly"  as  it  moves 
over  a  fixed  surface.  These  ideas  once  clearly  grasped,  will 
enable  any  one  to  see  that,  underlying  the  apparent  unlikeness 
of  the  smoke-ring  to  a  living  amoeboid  vortex,  there  is  in  reality 
a  fundamental  similarity.  The  kind  of  "contractility"  which  is 
exhibited  by  an  amoeboid  is  thus  also  seen  to  be  fundamentally 
different  in  nature  from  that  presented  by  a  muscle,  in  which 
contraction  is  conditioned  by  a  vastly  more  complex  structure. 
When  an  Amoeba  passes  into  the  resting  stage  its  plasma  is 
very  apt  to  assume  an  almost  perfectly  globular  form.  Its 
pseudopodia  are  retracted  ;  its  surface  becomes  smooth,  and 
the  whole  organism  passes  into  the  almost  homogeneous, 
quiescent  or  lethargic  condition  of  a  ball  of  protoplasm  that  no 
longer  manifests  its  characteristic  types  of  motion  and  irrita- 
bility, at  least  externally.  Unequal  surface-tensional  disturb- 
ances no  longer  affect  it  ;  it  is  now  under  the  domination  of 
the  same  physical  influences  that  determine  the  globular  form 
of  a  sphere  of  oil  in  a  mixture  of  alcohol  and  water  of  the  same 
specific  gravity  as  itself.  Its  cytoplasmic  substance  is  nearly 
or  quite  homogeneous,  and  the  excessively  slow  and  torpid  meta- 
bolic processes,  within  the  protoplasmic  mass  of  the  Amoeba, 
now  secrete  or  pour  out  a  cuticle  or  envelope  over  its  surface 
and  in  which  the  organism  is  said  to  be  "encysted."  All  of 
these  processes  are  purely  dynamical,  just  as  were  all  of  those 
associated  with  the  motion  of  the  organism.  Not  only  are  all 
of  these  processes  dynamical,  but  all  are  also  directly  "adap- 
tive," in  virtue  of  the  fact  that  the  equilibria  successively 
attained  are  merely  a  quantitative  dynamical  response  from 
within  a  "living  "  molecular  mechanism  to  a  change  in  external 
energy-conditions.  All  "  adaptation  "  is  to  be  so  interpreted, 
so  that  "natural  selection"  may  be  at  last  resolved  into  pure 
energy-factors,  and   thus  brought   into  coordination  with    the 


8o  BIOLOGICAL   LECTURES. 

rest  of  the  forces  of  the  cosmical  universe.  The  mischievous 
metaphor,  ''  natural  selection,"  has  blinded  many  naturahsts  to 
the  real  meaning  of  this  expression. 

In  the  same  way  we  may  discuss  the  characters  of  other 
amoeboids.  Each  is  found  to  have  its  own  kind  of  plasma, 
that  behaves  differently  in  each  species.  Some  move  more 
rapidly  than  others,  some  have  blunt,  others  long,  slender  or 
attenuated  pseudopodia  ;  some  may  have  bent  pseudopodia,  or 
have  the  axes  of  their  straight  pseudopodia  normal  to  the  sur- 
face of  the  spherical  body  of  the  organism  ;  others  obey  a 
different  rule  in  this  respect.  In  some  the  plasma  is  clear, 
in  others  more  opaque  ;  in  some  the  nucleus  is  globular,  in 
others  flattened.  Thus  one  might  go  on  and  show  that  the 
different  proportions  and  behaviors  of  the  same  parts,  in  dif- 
ferent species,  was  evidence  that  totally  different  molecular 
mechanisms  were  simply  making  their  necessarily  different 
responses  to  the  same  environment,  because  of  differences 
in  the  physical  and  chemical  properties  of  their  constituent 
plasma.  Herein,  probably,  also  lies  the  whole  secret  of  the  dif- 
ference of  power  presented  by  the  germs  of  different  creatures. 
They  develop  as  they  do  in  the  case  of  each  species,  because 
of  their  specific  chemical  constitutions,  and  not  because  there 
are  a  lot  of  ''biophores,"  '^gemmules,"  etc.,  ''superintending" 
the  business  of  development  in  a  particular  way  during  the 
evolution  of  the  ^gg  of  each  form.  The  preposterous  assump- 
tion that  enough  energy  can  be  squeezed  into  an  ^^g  poten- 
tially to  carry  the  materials  into  place  that  are  assimilated  during 
development  in  order  to  build  an  elephant,  for  example,  is 
worthy  of  mediaeval  philosophers,  but  not  of  those  of  the  close 
of  the  nineteenth  century.  Every  form  of  energy,  including 
that  of  "life,"  is  correlated,  and  is  amenable  to  the  same  laws. 
Full  knowledge  of  the  mode  of  operation  of  the  material 
energy-complexes  that  we  call  ''living,"  will  disclose  the  true 
theory  of  morphology  and  the  true  meaning  of  life  as  well. 

These,  here  incompletely  reported,  observations  make  it  toler- 
ably clear  that  amoeboid  motion  is  worth  studying,  in  order  to 
get  clear  notions  of  how  living  motions  and  energies  are  oper- 
ative in  one  of  the  simplest  organisms  known  to  the  zoologist. 


DYNAMICS  IN  EVOLUTION.  8 1 

They  also  make  it  very  evident  that  observers  have  hitherto 
allowed  purely  morphological  considerations  to  becloud  their 
vision.  In  order  to  discover  the  meaning  of  the  morphology 
of  the  simplest  organisms,  their  actions  must  be  subjected  to 
the  most  searching  analysis.  These  observations  have  proved 
that  the  functions  of  an  organism  are  also  functions  of  its  form. 
It  has  been  pretty  clearly  established,  by  what  has  been  said 
above,  that  every  action  of  the  Amoeba  was  followed  by  a  mor- 
phological change.  In  the  belief  that  this  same  thing  holds 
good  throughout  the  whole  animal  and  vegetable  world  under 
most  complexly  interacting  energy-conditions,  I  will  predict 
what  I  believe  will  yet  be  possible,  viz.,  the  discovery  of  the 
true  causes,  in  detail,  of  the  forms  of  all  organized  existences. 
In  order,  however,  to  accomplish  this  end,  the  following  will 
first  have  to  happen,  namely,  an  abandonment  of  all  hitherto 
accepted  hypotheses  of  inheritance,  a  new  conception  of  the 
nature  of  life,  new  views  of  the  nature  of  the  process  of  natural 
selection,  and,  above  all,  the  abandonment  of  all  such  concep- 
tions as  gemmules,  biophores,  pangenes,  plastidules,  plassomes, 
etc.,  and  the  admission  that  the  phenomena  of  life  are  ulti- 
mately physical  in  their  nature  and  are  to  be  treated  in  detail 
as  physical  problems. 

It  is  now  my  firm  conviction,  also,  that  experimental  investi- 
gation in  embryology  will  make  no  solid  progress  until  the 
foregoing  prepossessions  are  abandoned,  or  until  the  mischiev- 
ous influence  of  such  speculations  and  their  kindred,  as  those 
regarding  a  *' germ-plasm,"  etc.,  have  been  entirely  eradicated 
from  the  minds  of  the  present  generation.  In  conclusion, 
let  me  remark  that  five  sciences  are  indissolubly  connected 
together  in  the  study  of  the  fundamental  problems  of  life; 
these  are  :  physics,  chemistry,  physiology,  morphology,  and 
psychology.  When  each  of  these  sciences  shall  have  been 
given  its  due  weight  and  place  in  the  conduct  of  the  study  of 
life-forms,  we  shall  begin  to  know  what  the  latter  really  mean, 
but  not  until  then. 


FIFTH   LECTURE. 


ON  THE  NATURE  OE  CELL-ORGANIZATION.i 

S.  WATASE. 
I. 

If  the  true  nature  of  a  higher  organism  cannot  be 
understood  without  considering  the  structure  and  the  function 
of  its  component  organs,  it  is  equally  certain  that  the  nature 
of  an  individual  cell  cannot  be  made  intelligible  without  a 
comprehensive  study  of  the  different  organs  of  which  it  is 
composed. 

At  the  present  time,  when  morphologists  are  explaining 
the  origin  and  development  of  the  different  structures  in  an 
organism  in  terms  of  cell-growth  and  of  cell-metamorphosis, 
and  when  physiologists  are  referring  the  activities  of  the  whole 
organism  back  to  the  functions  of  its  component  cells,  it  is 
natural  that  considerable  attention  should  now  be  directed 
toward  the  solution  of  more  elementary  problems  concerning 
the  nature  of  the  cell-organism.  The  cell-theory,  while  it 
explains  the  structure  and  functions  of  a  tissue  on  a  cellular 
basis,  leaves  the  real  nature  of  the  cell  itself  unexplained. 

The  vital  properties  of  a  nucleated  cell  manifest  themselves 
in  various  ways,  but  they  may  be  broadly  classified  under  two 
categories,  viz.,  (i),  those  tending  to  the  preservation  of  the 
individual  cell,  and  (2),  those  tending  to  the  maintenance  of 
the  species.  Under  the  first  are  included  the  general  phe- 
nomena of  cell-metabolism  and  different  forms  of  irritability, 
and  under  the  second  those  of  cell-division  and  cell-fusion. 

Diverse  as  are  these  special  cell-phenomena  which  tend 
directly  or  indirectly  to  the  preservation  of  the  cell,  it  must 

1  Lecture  given  before  the  Biological  Club  of  the  University  of  Chicago, 
February  7,   1893,  ^^^^  afterward  written  out  in   the  present  form. 


84  BIOLOGICAL   LECTURES. 

be  admitted  that  their  real  significance  can  only  be  under- 
stood when  each  is  taken  in  connection  with  the  others, 
the  tout  e7isemble  of  which  form  the  life  of  the  nucleated 
cell.  If  any  explanation  of  special  phenomena  be  attempted, 
it  should   be  in  the   light   of   what  we  know  of  the  whole. 

We  do  not  gain  much,  however,  by  so  saying,  as  long  as 
this  knowledge  of  the  whole  is  merely  a  name  for  the  sum 
total  of  incoherent  observations  on  diverse  cell-phenomena. 
Beneath  and  beyond  all  vital  manifestations  of  a  cell,  there 
must  exist  a  primary  physiological  condition,  on  which  the 
details  of  secondary  cell-phenomena  depend.  Just  what  con- 
stitutes the  primary  physiological  phenomenon  of  the  cell, 
is  the  point  that  I  wish  to  discuss  in  the  present  paper, 
believing,  as  I  do,  that  such  a  problem  as  that  of  cell-organ- 
ization, can  be  approached  from  the  functional  side  with 
better  effect  than  has  thus  far  been  attained  from  the  side  of 
pure  morphology. 

Before  we  proceed  further,  it  may  not  be  out  of  place  here 
to  introduce  a  general  schematic  description  of  a  nucleated 
cell.i 

Excluding  the  centrosome  and  chromatophore  for  the  present, 
an  animal  cell  may  be  described  as  composed  of  two  sharply 
distinct  organs  :  the  cell-body  {cytosoinc),  and  the  nucleus 
{caryosoine). 

The  nucleus,  in  its  ''resting  stage,"  has  a  definite  membrane  ^ 
around  it,  called  the  nuclear  membrane  or  caryothcca.  The 
cell-body  consists  of  a  net- work  of  cytoplasm.  This  net-work 
contains  within  its  own  substance  small  bodies  of  varying 
sizes,  which  are  known  as  the  microsonics  or,  more  strictly, 
the  cytomici'osonics.  Surrounding  the  cytosome,  there  is  a 
membrane  known  as  the  cell-membrane  or  cytotheca.  It  may 
exist  as  a  thickened  border  of  the  cytosome  or  as  a  distinct 
membrane  separated  from  the  cytosome. 

1  The  descriptive  cytological  terms  adopted  here  have  merely  an  anatomical 
significance,  and  do  not  refer  to  the  chemical  or  functional  properties  of  the  struc- 
ture. Several  terms  recently  used  by  Haeckel  [Anthropogeiiie,  4th  edition,  Leipzig, 
1891),  have  therefore  been  found  most  convenient.  Only  the  more  salient  features 
of  the  cell  will  be  emphasized  in  this  place,  that  being  sufficient  for  our  present 
purpose. 


ON   THE   NATURE    OE   CELL-ORGANIZATfON.  85 

The  meshes  of  the  cytoplasm  are  filled  with  a  fluid  sub- 
stance, commonly  called  the  cytoplasmic  fluid,  or  to  use 
Haeckel's  term,  the  cytolympJi. 

The  cytoplasm  is,  however,  the  only  living  portion  of  the 
cell-body,  and  hence  properly  belongs  to  the  category  of 
protoplasm  in  the  more  strict  technical  sense  of  the  term.  The 
cytolymph  is  the  inert,  passive,  non-living  portion  of  the 
cell-body.  Besides  the  cytolymph,  there  usually  exist  a  number 
of  non-living  bodies  in  the  cell-body,  as  yolk-granules,  oil  drops, 
debris  of  food,  zymogen  granules,  etc.,  according  to  the  nature 
of  different  cells.  These  non-living  substances  altogether 
belong  to  the  group  known  as  victaplasin  or  paraplasm^  in 
contradistinction  to  the  substance  which  is  the  real  living 
element  of  the  cell  —  the  protoplasm. 

The  contents  of  the  nucleus  {caryosome)  may  be  arranged 
also  into  two  .similar  groups  of  living  and  non-living  elements. 
The  cJiromosome  is  distinctly  protoplasmic  in  character,  and  so 
is  the  fine  net-work  of  the  ''achromatic"  thread-like  substance 
which  is  often  found  traversing  the  nuclear  cavity.  In  several 
cases,  if  not  in  all,  these  filaments  are  the  actual  continuation 
of  the  cytoplasmic  net-work  existing  around  the  nuclear 
membrane. 

The  fluid  substance  which  bathes  these  semi-solid  living 
constituents  of  the  nucleus  is  known  as  nuclear  fluid  or  caryo- 
lympJi.  In  the  caryolymph  there  exists  a  body  known  as  the 
nucleolus.  In  certain  cases,  the  filaments  of  the  chromosome 
have  been  found  passing  through  the  substance  of  the  nucleolus 
or  directly  ending  in  it.  Sometimes  only  one  nucleolus  exists 
in  each  nucleus,  while  in  other  cases  over  .one  hundred  nucleoli 
may  be  found  in  one  nucleus.  The  number  of  nucleoli  is  quite 
variable  in  different  cells,  but  fairly  constant  in  a  given  species 
of  cell.  The  nucleolus  is  not  a  permanent  body  in  the  nucleus. 
It  may  exist  at  one  stage  of  the  cell,  and  may  disappear  at  the 
next.  The  micro-chemical  reaction  of  the  nucleolus  is  entirely 
different  from  that  of  the  chromosome.  It  appears  probable 
that  three  or  more  different  bodies  are  included  under  the 
same  name  of  nucleolus.  Indeed,  one  sees  no  reason  why  the 
inside  of  the  nuclear  membrane  may  not  be  used  as  a  deposi- 


86  BIOLOGICAL   LECTURES, 

tory  for  some  solid  products  of  cell-metabolism,  under  certain 
circumstances,  just  as  the  spaces  in  the  cell-body  are  used  for 
such  a  purpose.  And  thus  some  of  the  bodies  included  under 
the  generic  name  of  nucleolus,  may  belong  to  the  group  of 
metaplasm.  It  is,  however,  difificult  to  pass  any  definite 
opinion  on  the  nature  of  the  nucleolus  at  the  present  stage 
of  our  knowledge  on  the  subject. 

To  recapitulate  briefly,  then,  the  chromosome  and  cyptoplasm 
are  the  two  active,  living  constituents  of  the  cell.  The  rest  of 
the  bulk  of  a  cell  consists  of  non-living  substances,  which  have 
yet  to  be  converted  into  vital  elements,  or  are  the  products  of 
metabolism  which  have  now  lost  the  distinctive  characteristic 
of  a  living  substance. 

The  behavior  of  the  cytoplasmic  thread  or  network  suggests 
that  it  is  formed  of  a  group  of  small,  living  particles,  each 
with  the  power  to  assimilate,  to  grow  and  multiply  by  division. 
The  chromosome,  in  the  .same  way,  is  itself  a  colony  of 
minute  organisms  of  another  kind,  each  endowed  with  similar 
attributes  of  vitality.  The  media,  in  which  they  live, — the 
cytolymph  and  caryolymph  —  are  the  media  in  which  they 
breathe,  from  which  they  derive  their  nourishment,  or  within 
which  they  deposit  the  products  of  their  metabolism.  The 
reason  why  the  cell  as  a  whole  assimilates,  grows  and  divides, 
is  ultimately  due  to  the  fact  that  the  minute  particles  whiA 
compose  the  cytoplasm  and  chromosome  are  endowed  with 
these  functions. 

Keeping  in  mind  then  such  a  simple  nucleated  cell  like 
an  amoeba  or  an  animal  ovum,  as  a  type,  let  us  ask  ourselves 
the  following  questions  :  What  is  the  relation  of  nucleus^  to 
cytoplasm,  and  of  cytoplasm  to  nucleus  in  a  cell .''  What  is 
the  significance  of  this  duplex  morphological  organization } 
Through  what  process  may  such  an  organization  as  the 
nucleated  cell  be  considered  to  have  come  into  existence.? 

The  biogenetic  law  as  applied  to  the  study  of  metazoan 
organisms,  has  been  an  important  instrument  of  research  in  the 
field  of  comparative  anatomy  and  embryology,  but  it  is  hard  to 

1  In    the   following,    the    word    "  nucleus "   is    used,    unless    otherwise    stated, 
synonymous  with  its  essential  constituent,  the  "  chromosome." 


ON   THE   NATURE    OE  CELL-ORGAN/ZATfy>^j  ^r  yi^j 

use  it  as  a  working  theory  in  the  explanation  of  cellular 
phenomena  such  as  I  have  already  indicated.  For  it  is  possible 
that  the  law  followed  by  the  cell-aggregate  in  the  course  of  its 
development,  may  not  have  been  followed  in  the  formation  of 
the  individual  cell. 

It  is  perfectly  conceivable  that  the  process  by  which  the  cell 
was  first  formed  may  have  been  due  to  causes  of  special 
character,  while  the  conversion  of  the  cell  thus  formed,  into  an 
organism  of  higher  complexity,  may  have  been  due  to  causes 
entirely  different  from  those  that  operated  in  the  production  of 
the  nucleated  cell. 

There  is  no  necessary  reason  to  conclude,  as  has  been  done 
by  several  naturalists,  that  because  the  complex  organism 
develops  by  a  process  of  differentiation  of  the  homogeneous 
germ,  the  duplex  structure  of  the  cellular  units  which  compose 
the  organism,  must  have  also  had  a  parallel  course  of  develop- 
ment from  its  antecedent  germ. 

It  is  this  point  that  I  wish  to  discuss  more  in  detail  in  the 
following. 

II. 

The  parts  of  a  living  organism  commonly  termed  its  organs 
may  be  studied  from  three  points  of  view  :  — 

1.  How  far  are  these  parts  adapted,  by  their  form  and 
structure,  to  perform  their  physiological  work }  This  mode  of 
studying  the  organs  belongs  to  physiology. 

2.  Where  and  how  do  they  arise  in  a  given  organism  ?  This 
field  of  study  is  a  branch  of  morphology. 

3.  If  the  morphological  study  of  the  organ  be  extended 
through  organisms  of  different  grades  of  complexity,  it  may 
enable  us  to  infer  the  probable  steps  through  which  the  given 
organ  may  have  passed  in  the  course  of  its  phylogenetic  history. 

When  these  three  modes  of  study  as  pursued  by  naturalists 
at  the  present  day,  are  applied  to  the  study  of  organs  of  an 
individual  cell,  it  resolves  itself  into  three  problems  :  — 

I.  How  far  are  nucleus  and  cytoplasm  adapted  by  their  form 
and  structure,  to  perform  their  physiological  work  in  a  given 
cell } 


8i8|      ^^v-  BIOLOGICAL    LECTURES. 

2.  In  what  manner  do  they  originate  in  a  given  cell  ?  This 
ultimately  resolves  itself  into  the  problem  of  cell-division 
{Cytomci')')  on  the  one  hand  and  cell-fusion  on  the  other. 

3.  What  are  the  probable  steps  in  the  ancestral  history,  by 
which  these  structures  came  into  existence  ?  This  belongs  to 
the  broad  question  of  Cytogciiy  as  understood  in  its  phylogenetic 
sense. 

In  following  out  these  questions  more  in  detail,  it  is 
important  to  bear  in  mind  at  the  outset,  some  vital  distinctions 
involved  in  the  use  of  the  term  oj'gaii,  whether  we  understand 
it  in  a  \>\\YQ\y  physiological,  or  in  a  morphological  sense.  From 
the  purely  physiological  standpoint,  any  structure  or  member 
which,  by  its  activity,  contributes  to  the  general  welfare  of  the 
whole  organism  is  an  organ,  whether  that  structure  may  have 
originated  primarily  in  the  organism, 'or  may  have  been  derived 
secondarily  from  an  external  source.  Thus,  the  chromatophores  ^ 
in  the  leaves  of  a  plant  are  the  organs  of  assimilation  in  that 
plant  ;  the  '*  gonidia  "  in  the  thallus  of  a  lichen  are  the  organs 
of  a  lichen,  in  a  physiological  sense  as  the  heart  or  lung  is  the 
organ  in  the  body  of  a  higher  organism. 

But  from  the  morphological  side  of  the  case  it  is  different. 
According  to  the  morphological  view,  every  diffcreiitiatfd 
orgajiisvi,  every  organism  composed  of  orgajis,  can  only  have 
originated  from  a  homogeneous  stage  by  the  differentiation  of 
its  parts.  To  state  this  in  another  way,  "however  complicated 
one  of  the  higher  animals  and  plants  may  be,  it  begins  its 
separate  existence  under  the  form  of  a  nucleated  cell.  This, 
by  division,  becomes  converted  into  an  aggregate  of  nucleated 
cells  :  the  parts  of  this  aggregate,,  following,  different  laws  of 
growth  and  multiplication,  give  rise  to  the  rudiments  of  the 
organs  ;  and  the  parts  of  these  rudiments  again  take  those 
modes  of  growth  and  multiplication  and  metamorphosis  which 
are  needful  to  convert  the  rudiment  into  the  perfect  structure."  ^ 

1  The  term  chroniatophore  (Schmitz)  is  here  used  in  a  broad  sense,  including 
leucoplasts  and  the  various  coloring  substances  in  the  flower  and  the  fruit,  as  well 
as  the  chrophyll  granules  in  the  leaves  of  a  green  plant.  The  term  is  synonymous 
with  Arthur  Meyer's  trophoplast  and  Schimper's  plastid. 

2  T.  H.  Huxley  :  Article  Biology,  Encyclopaedia  Britannica,  9th  edition,  Vol.  Til, 
p.  682,  1878. 


ON   THE   NATURE    OF   CELL^ORGANIZ AT/ON  89 

Now,  this  morphological  criterion  of  an  organ,  which 
necessarily  relates  to  the  history  and  mode  of  its  origin  wit/iiti 
the  orgaiiisDi,  by  the  differentiation  of  its  parts,  does  not  apply 
to  the  chromatophore  in  a  green  plant,  nor  to  the  "gonidia" 
in  a  lichen  thallus,  although  there  can  be  no  doubt  whatever 
that  these  structures  serve  as  organs  in  the  physiological  sense, 
in  the  respective  organisms.  The  chromatophores  are  not 
the  products  of  differentiation  of  an  homogeneous  germ  of 
the  plant.  They  can  only  originate  by  the  division  of  pre- 
existing chromatophores,  if  we  follow  such  botanists  as  Schmitz, 
Schimper  and  Meyer. ^  The  colorless  protoplasm  of  the  plant 
and  the  chromatophores  are  the  coexistent  but  independent 
structures,  with  no  genetic  connection  between  them. 

In  the  organization  of  a  lichen,  the  case  is  clearer  and  more 
to  the  point  of  our  inquiry.  As  is  well  known,  the  "gonidia" 
and  their  supporting  meshwork  are  derived  from  two  different 
groups  of  plants,  viz.,  Algce  and  Fungi,  respectively,  although 
their  physiological  adaptation  to  each  other  is  so  perfect,  so 
much  so,  in  fact,  that  in  several  lichens  the  hyphae  of  the 
fungus  cannot  live  when  separated  from  the  algal  portion,  the 
"gonidia."  Here,  again,  it  is  needless  to  say  that  these  two 
organs  are  not  the  products  of  differentiation  from  some  homo- 
geneous an/age  as  different  organs  are  in  one  of  the  complex 
animals.^  On  the  other  hand,  the  *'gonidia"  of  one  individual 
lichen  are  genetically  related  to  the  "gonidia"  of  another,  and 
not  at  all  to  the  hyphae  of  the  thallus.  In  a  similar  way  the 
hyphae  of  one  individual  lichen  are  genetically  related  to  the 
hyphae    of    another    lichen   of    the   same   species,   and    not    to 

1  Schmitz  :  Die  Ckromatophoren  Jer  Algen,  Bonn,  1882.  Schimper  :  Ueher  die 
Entwickelung  der  Chlorophyllkoriier  und  Far/>korfer,  Bot.  Zeit.,  1883,  41.  Jahrg. 
Meyer  :  Ueber  Krystalloide  der  Trophoplaslen  iind  i'tber  die  Chromoplasten  der 
Angiospermeu,  Bot.  Zeit.,  1883,  41.  Jahrg. 

2  Before  the  discovery  of  the  true  nature  of  lichens,  it  was  thought  that  both 
"  gonidia  "  and  supporting  fungal  hyphae  were  the  products  of  development  of  a 
single  germinating  spore.  "  Gonidia,"  which  are  the  symbiotic  algal  cells,  were 
supposed  to  be,  as  the  term  indicates,  asexual  organs  of  reproduction  produced 
from  the  hyphae  and  capable  of  development  into  a  new  and  perfect  lichen-thallus. 
The  view  that  hyphae  might  also  be  produced  from  the  "gonidia"  was  often 
expressed.  De  Bary,  Historical  Notice  of  the  Lichens.  Comp.  Morphology  and 
Biology  of  Fungi,  etc.,  p.  416. 


90  BIOLOGICAL   LECTURES. 

the  "gonidia,"  with  which  they  live  in  close  symbiotic  rela- 
tions.^ 

Thus  the  morphological  and  physiological  consideration  of 
an  organ,  such  as  we  have  just  given,  leads  us  to  conclude  that 
when  we  find  two  structures  in  an  individual  organism  most 
intimately  associated  in  their  physiological  relationship,  it  does 
not  necessarily  follow  that  they  are  organs  in  the  morphological 
sense  also.  The  history  of  the  lichen  clearly  shows  that  an 
independent  organism,  composed  of  organs^  can  be  created  by  the 
union  of  tivo  dissimilar  organisms  by  the  establishment  of  an 
intimate  physiological  relationship  between  them.  In  fact,  a 
certain  number  of  species  of  lichens  have  been  actually  pro- 
duced by  bringing  fungi  and  algae  together  in  a  synthetic  way.^ 
The  fungus  and  alga,  by  the  interchange  of  their  metabolic 
products,  supply  the  nutritive  wants  of  each,  and  thus  produce 
the  autonomous  whole  which  can  exist  in  places  where  neither 
the  alga  nor  the  fungus  would  be  able  to  exist  separately. 

In  dealing  with  the  structures  in  an  organism  commonly 
called  organs,  I  repeat,  we  must  clearly  bear  in  mind  whether 
the  structure  in  question  is  an  organ  in  the  physiological  and 
morphological  senses,  or  whether  it  is  an  organ  simply  in  ^he 
physiological  sense.  If  the  structure  is  an  organ  in  the  mor- 
phological sense,  the  study  of  the  development  of  the  whole 
organism  will  show  that  it  is  a  part  of  the  products  of  differ- 
entiation of  some  preexisting  germ  from  which  the  entire 
organism  was  derived  ;  if  it  be  an  organ  in  a  purely  physio- 
logical sense  alone,  there  will  be  no  genetic  connection  between 
the  different  structures,  although  each  is  indispensable  to  the 
existence  of  the  other.  In  short,  the  perfection  to  ivJiicJi  the 
physiological  adaptation  of  different  orgaits  is  canned  out  in  a 
given  organism,  is,  in  itself,  no  proof  that  they  ivei'e  derived 
by  the  diffeirntiation  of  some  common  germ  ;  but,  on  the  con- 
trary,  tivo   dissimilar  organisms   may,    by   mutual  adaptation, 

1  In  using  the  term  "  symbiotic,"  to  express  the  relation  between  the  alga  and 
fungus  in  the  organism  of  a  lichen,  I  simply  follow  such  botanists  as  De  Bary 
(Z>?>  Erscheinung  der  Symbiose,  Strassburg,  1879,  p.  15,  et  seq.),  Frank  {Sytnbiose, 
Lehrbiich  der  Botanik,  Bd.  I,  1892,  Leipzig),  and  others. 

-  See,  for  example,  the  recent  work  by  Bonnier,  Recherches  sur  la  syiithese  des 
lichens.     Ann.  des  sc.  nat.,  7^2  serie,  IX,  Botanique,  1889. 


ON   THE   NATURE    OF   CELL-ORGANIZATION  91 

give  rise  to  a  third  organism  in  wJiich  eaeh  of  them  serves  as 
an  organ  to  the  luhole. 

It  is  needless  to  say  that  almost  all  structures  in  higher 
organisms  ^  are  derived  by  the  differentiation  of  some  pre- 
existing germ,  but  at  the  same  time  it  is  important  to  bear  in 
mind  that  this  is  not  always  the  case,  particularly  in  the  lower 
forms.  It  is  this  consideration  which  interests  us  particularly, 
as  it  may  be  the  key  to  the  interpretation  of  the  organization 
represented  by  the  single  nucleated  cell. 

III. 

The  permanent  organs  of  the  cell  are,  following  the  recent 
exposition  of  Strasburger,^  considered  to  be  (i)  Cytoplasm, 
(2)   Nucleus,   (3)   Centrosome,   (4)   Chromatophore. 

The  last  named  structure  occurs  normally  in  the  cells  of 
green  plants,  and  sometimes  in  those  of  animals.^     Following 

1  If  Riickert's  observation  {(Jber  physiologische  Polyspermie  bei  vieroblastischen 
Wirbeltiereiern,  Anat.  Anzeiger,  Bd.  VII,  1892)  that  in  a  certain  vertebrate  the 
merocyte-nuclei  come  from  the  nuclei  of  the  supernumerary  sperm-cells  which 
enter  the  ovum,  be  confirmed,  it  would  seem  that  a  part  of  one  important 
embryonic  organ,  in  an  organism  like  Torpedo,  is  bodily  derived  from  the  outside 
source. 

2  E.  Strasburger  :    Das  Protoplasmaiind  die  Reizbarkeit,   1891,  Jena. 

3  See  in  this  connection,  Lankester's  article  Animal  Chlorophyll  (Nature,  vol.  44, 
1 891)  which  is  the  review  of  G.  Haberlandt's  paper  Ueber  den  Ban  und  die  Bedeu- 
tung  der  Chlorophyllzellen  von  Convoluta  Roscoffensis,  in  von  Graff's  Die  Organi- 
sation der  Turbellaria  accela,  1891,  Leipzig.  I  have  not  been  able  to  see 
Haberlandt's  original  paper.  Haberlandt  suggests,  to  quote  Prof.  Lankester, 
"that  while  phylogenetically  they  [chlorophyll-cells  in  Convoluta^  must  be  regarded 
as  Algae  (that  is  to  say,  have  descended  from  Algae)  yet  at  the  present  time  they 
have  by  profound  adaptation  to  life  in  and  with  the  Convoluta^  altogether  lost 
their  character  as  algal  organisms,  and  have  become  an  integral  histological 
element  of  the  worm,  and  in  fact  constitute  its  assimilation  tissue.  .  .  .  Haber- 
landt is  inclined  to  place  his  theory  as  to  the  green  cells  of  Convoluta  alongside 
the  suggestion  of  Schimper  as  to  the  origin  of  the  chlorophyll  corpuscles  of  higher 
plant  —  namely,  that  these  are  due  to  the  union  in  the  remote  past  of  a  green 
colored  with  a  colorless  organism." 

.Schimper  has  shown  that  the  chromatophores  (Schimper's  plastids)  are  formed 
by  the  division  of  the  preexisting  chromatophores,  and  not  by  the  differentiation 
of  the  cell-protoplasm.  Schimper's  view  referred  to  above  on  the  origin  of  the 
chlorophyll  bodies  in  the  plant  cells  may  be  gathered  from  the  following  quota- 
tions :  "  Sollte  es  sich  definitiv  bestatigen,"  says  Schimper,  "  dass  die  Plastiden  in 
den  Eizellen  nicht  neu  gebildet  werden,  so  wiirde  ihre  lleziehung  zu  dem  sie 
enthaltenden  Organismus  einigermassen  an  eine  Symbiose  erinnern.      Moglicher- 


92  BIOLOGICAL   LECTURES. 

the  views  held  by  Schmitz,  Schimper  and  others,  we  have 
already  regarded  this  structure  as  an  organ  totally  independent 
of  the  colorless  protoplasm  of  the  green  plant.  In  regard  to 
the  centrosome,  aside  from  its  apparent  function  during  the 
division  of  the  nucleus,  we  know  very  little  to  justify  our 
discussion  in  the  present  connection.  Personally,  I  cannot 
agree  with  those  who  place  the  centrosome  in  the  same  category 
of  the  permanent  cell-organs  as  the  nucleus.  On  the  other 
hand,  I  believe  that  the  centrosome  is  a  special  form  of  the 
cytomicrosome,  which  exists  almost  in  every  part  of  the  cell. 
For  the  reason  of  this  homology  of  the  centrosome,  I  may 
refer  the  reader  to  my  former  paper. ^ 

weise  verdanken  die  griinen  Pflaiizen  wirklich  einer  Vereinigung  eines  farblosen 
Organismus  mit  einem  von  Chlorophyll  gleichmassig  tingirten  ihren  Ursprung." 
(Schimper  :  Ueber  die  Eutwickcliing  der  Chlorophyllkorucr  und  Farbkorper,  Bot. 
Zeit.,  41.  Jahrg.,  1883,  pp.  111-112.)  Schimper  supports  this  statement  by  quoting 
Reinke  (Allg.  Botanik,  p.  62),  who  states  that  the  chlorophyll  bodies  in  the 
decomposing  cells  of  a  cucumber  attacked  by  a  certain  fungus,  still  continued  to 
grow  and  multiply. 

In  view  of  the  fact  that  there  exists  a  close  analogy  between  the  nucleus 
and  the  chromatophore  (see  Schmitz,  Die  Chrofnatop/wren  da^Algcn,  Bonn,  1882, 
p.  167),  the  observations  by  Metschnikoff  and  Soudakewitch  {La  phagocytose 
musculaire ;  contribution  a  V etude  de  V injiamviation  parenchyjnateiise.  Annales  de 
rinstitut  Pasteur,  6me  Annee,  No.  i,  Janvier,  1892,  pp.  1-20,  Pis.  I-III),  on  the 
repeated  division  of  the  muscle  nuclei  in  the  debris  of  degenerating  muscle  fibres 
which  originally  constititted  a  part  of  their  cytoplasm,  in  the  course  of  muscle 
degeneration,  may  be  interpreted  in  the  same  way  as  Schimper  did  of  Reinke's 
observation  on  the  behavior  of  the  chlorophyll  bodies  in  the  decomposing  vegetable 
tissue  referred  to  above. 

For  the  view  that  considers  the  animal  chlorophylls  as  the  veritable  Algae,  see 
the  well-known  papers  by  Gesa-Entz  and  K.  Brandt.  Felix  le  Dantec,  in  his 
recent  paper,  Kecherches  sur  la  symbiose  des  algues  et  des  protozoaires  ( Annales  de 
I'Institut  Pasteur,  t.  VI,  No.  3,  1892),  has  brought  further  experimental  evidence 
in  support  of  the  view  that  the  chlorophyll  corpuscles  in  an  animal  organism  as 
Paramcecium,  are  the  symbiotic  Algae.  I  mention  these  simply  to  call  attention 
once  more  to  the  fact  that  certain  parts  of  an  organism,  which  were  originally 
considered  to  be  integral  elements  of  the  organism,  derived  by  the  differentiation 
of  the  germ,  have  been  shown  to  be  due,  in  reality,  to  a  secondary  association  of 
two  or  more  different  orga^iisms,  originally  separate  and  independent,  and  what 
we  call  organs  from  the  physiological  side,  in  such  an  organism,  are  in  reality 
organisms  by  themselves. 

1  S.  Watase  :  Homology  of  the  Centroso?ne,  Journal  of  Morphology,  Vol.  VIII, 
Pt.  2,  1893.  A.  Brauer  {Zur  Kentitniss  der  Herkunft  des  Centrosomas,  Biol.  Central- 
blatt,  Bd.  XIII,  Nr.  9  u.  10,  May,  1893),  ^^^  recently  come  to  the  conclusion  that 
in  the  spermatocyte  of  A  scar  is  megalocephala,  variety  univalens,  the  centrosome 


ON   THE   NATURE    OF  CELL-ORGANIZATION.         93 

If,  therefore,  I  omit  from  consideration  the  chromatophore 
and  the  centrosome  in  the  following,  it  is  because  the  former 
has  been  fully  treated  by  able  botanists,  and  the  latter  is 
not  sufficiently  known,  to  my  knowledge,  to  admit  of  useful 
discussion  in  connection  with  our  subject.  If,  however,  the 
centrosome  be  shown  to  be  an  organ  of  the  cell,  contrary  to 
my  former  conclusion  above  alluded  to,  with  a  morphological 
significance  comparable  to  that  of  the  nucleus  or  the  cyto- 
plasm, the  inference  I  advance  in  regard  to  the  nature  of  the 
latter  organs  will  apply  equally  well  to  the  former. 

Confining  our  remarks,  then,  to  the  nucleus  and  the  cyto- 
plasm, we  may  first  ask  whether  the  nucleus  is  to  be  regarded 
as  an  organ  in  a  morphological  sense,  or  only  in  a  physiological 
one.  Are  nucleus  and  cytoplasm  products  of  differentiation 
from  some  homogeneous  milage  in  the  sense  that  all  morpho- 
logical organs  are,  or  may  not  their  constant  occurrence  in 
the  cell  rather  be  regarded  as  the  result  of  a  union  formed  in 
the  remote  past,  between  two  organisms  originally  independent 
and  dissimilar  —  a  union  of  such  a  kind  that  ages  of  mutual 
adaptations  have  rendered  their  independent  existence  no  longer 
possible }  Is  it  not  possible  to  regard  the  cell  as  a  symbiotic 
community,  in  which  the  cytoplasm  represents  one  group  of 

originates  in  the  inside  of  the  nuclear  membrane,  Brauer's  view,  however,  does 
not  militate  against  my  statement  that  the  centrosome  is  the  cyto-microsome  of  a 
gigantic  size,  and  that  wherever  cytoplasmic  net-work  exists  there  is  a  possibility 
of  developing  a  microsome.  When  the  centrosome  originates  inside  of  the 
nuclear  membrane,  it  may  be  said,  for  a  descriptive  purpose,  that  it  is  derived 
from  the  nucleus ;  when  it  originates  outside  of  the  nuclear  membrane,  such 
a  centrosome  may  be  said  to  be  cytoplasmic  in  its  origin.  Such  a  distinction  is 
purely  a  nominal  one,  however,  from  my  standpoint,  and  I  believe  the  general 
statement  that  all  centrosomes  are  cytoplasmic  in  their  origin  is  fundamentally  a 
correct  one.  Confusion  only  arises  when  we  do  not  keep  in  mind  the  fact  that 
the  cytoplasmic  net-work,  in  the  substance  of  which  the  microsome  and  centrosome 
arise,  exists  on  both  sides'  of  the  nnclear  membrane,  and  the  structure  kncnun  as 
nucleus,  contains  a  great  deal  of  cytoplasmic  substance  in  it. 

As  is  beautifully  shown  in  Brauer's  tnore  recent  paper  {Zur  Kcuntniss  der  Sper- 
matogenese  non  Ascaris  megaloeepAala^  Arc\\.  f.  mikr.  Anat.,  Bd;  42,  1893,  August, 
p.  1S5),  the  fact  that  in  one  variety  of  Ascaris  megaloccphala,  namely,  univalens^ 
the  centrosome  lies- inside,  and  in  another  variety,  bivaloi^,  outside  of  the  nuclear 
membrane,  is  enough,  to  my  mind,  to  show  that  it  is  the  substance  which  gives 
rise  to  the  centrosome,  and  not  the  position  where  the  centrosome  makes  its  first 
appearance,  which  we  must  consider  in  the  determination  of  its  honxoJogy. 


94  BIOLOGICAL   LECTURES. 

extremely  minute  organisms,  each  with  a  power  of  growing, 
assimilating,  and  dividing  ;  and  the  nucleus,  or,  more  strictly, 
the  chromosomes,  a  colony  of  still  different  forms,  each  with 
the  same  powers,  —  the  whole  making  an  organization  compar- 
able to  that  of  the  lichen,  which  is  composed  of  two  totally 
dissimilar  organisms  ? 

If  this  be  so,  then,  there  are  two  possible  ways  of  explaining 
the  nature  of  a  nucleated  cell  ;  viz.,  the  T/icojy  of  Differen- 
tiation, such  as  was  held  by  Haeckel,  Auerbach,  and  several 
others,  and  more  recently  by  Verworn  ^  and  Wiesner,^  and  the 
Theory  of  Symbiosis,  as  I  have  briefly  suggested. 

Let  us  examine  the  fundamental  phenomena  of  the  nucle- 
ated cell  from  the  standpoint  of  the  symbiotic  theory,  and, 
incidentally,  point  out  the  inadequacy  of  the  differentiation 
hypothesis  as  an  explanation  of  the  cell  phenomena  in  general. 

IV. 

Two  important  activities  in  the  developmental  phases  of 
protoplasmic  life^  ^.xq  cell-division,  e.g.,  caryokinesis,  and  cell- 
fusion,  e.g.,  fecundation.  In  both  cases,  the  identity  of  the 
nucleus  and  of  the  cytoplasm  is  never  once  lost  during  the 
whole  series  of  remarkable  changes.  There  is  a  continuity  of 
nuclear  matter  from  one  phase  to  another,  just  as  there  is  a 
continuity  of  the  cytoplasm  through  the  successive  j^eriods  in 
the  history  of  the  cell.  In  other  words,  the  nucleus  always 
originates  from  a  preceding  nucleus,  and  the  cytoplasm  from  a 
preceding  cytoplasm.  There  is  no  evidence  proving  that  the 
nucleus  is  formed  by  the  process  of  differentiation  from  the 
cytoplasm,  nor  that  the  cytoplasm  is  formed  by  the  differen- 

1  Max  Verworn:  Die  J)hysiologische  Bedejitiing  des  Zell-kerns,  Bonn,  189 1, 
p.   115. 

2  J.  Wiesner:  Die  Elementarstructur  tind  das  IVachsthiim  der  lebenden  Siibstaiiz, 
Wien,  1892,  p.  266. 

3  Following  the  suggestion  brought  out  by  Professor  Burdon  Sanderson  in  his 
discourse  on  the  elementary  problems  in  physiology  {Nature,  Vol.  XI,  Sept.  26, 
1889),  it  is  convenient  to  divide  the  protoplasmic  activities  into  two  main  groups 
—  the  developmental  and  the  non-developmental.  The  former  refers  to  those 
phenomena  of  the  cell  which  are  more  especially  connected  with  the  development 
or  unfolding  of  latent  character  of  the  germ,  and  the  latter  to  such  functions  as 
respiration,  secretion,  excretion,  etc. 


ON   THE   NATURE    OE   CELL-ORGANIZATION  95 

tiation  of  nuclear  substance.  The  developmental  history  of 
these  two  substances  naturally  leads  us  to  regard  them  as 
independent  structures,  although  each  is  necessary  to  the 
physiological  existence  of  the  other.  They  are  not,  therefore, 
morphological  organs  of  the  cell  in  the  sense  of  the  term  as 
we  have  explained  it.  Furthermore,  the  phenomena  of  division 
in  the  nucleus  and  cytoplasm  remind  us  forcibly  of  the  mode 
of  origin  of  the  soredia  in  the  lichen  ;  nor  is  this  remarkable,  if 
a  nucleated  cell  is,  like  the  lichen,  a  symbiotic  community  of 
two  dissimilar  organisms.  The  single  soredium  is  a  miniature 
lichen,  consisting  of  one  or  more  algal  cells  with  a  weft  of 
fungal  tissue  around  them.  The  algal  and  fungal  elements  in 
a  single  soredium  are  derived  from  the  corresponding  elements 
in  the  mother  lichen-thallus,  just  as  the  daughter  cell  derives 
its  nucleus  and  cytoplasm  from  the  corresponding  elements  in 
the  mother  cell. 

The  most  convincing  argument  proving  the  symbiotic 
character  of  a  lichen  consists  in  the  synthetic  production  of 
certain  species  of  lichens,  by  bringing  algal  and  fungal 
elements  together.  If,  therefore,  the  morphological  rela- 
tionship between  nucleus  and  cytoplasm  in  a  cell  is  that  of 
a  symbiotic  community,  the  fact  analogous  to  the  artificial 
synthesis  of  lichens  must  be  found  in  the  cell.  I  venture  to 
suggest  that  such  a  synthesis  of  a  living  cell  has  been  accom- 
plished. I  refer  to  Verworn's  ^  experiment  on  the  Radiolarian, 
Thalassicolla.  Verworn  took  three  vessels  of  equal  size,  and 
in  the  first  he  put  a  number  of  normal  TJialassicolla ;  in  the 
second,  he  put  one  which  had  its  central  capsule  with  its 
nucleus  removed  ;  in  the  third,  he  placed  an  individual  whose 
central  capsule  had  been  removed  and  replaced  by  the  trans- 
plantation of  the  central  capsule  of  another  individual  of  the 
same  species.  The  Radiolarian  in  the  third  vessel  was, 
therefore,  a  synthetic  one,  the  extra  capsular  protoplasm  lying 
outside  of  the  central  capsule,  being  derived  from  one  indi- 
vidual, and  the  central  capsule  itself,  with  its  nucleus,  being 
derived  from  another.  In  the  course  of  time,  the  Thalassi- 
colla which  had  lost  its  nucleus  by  the  removal  of  its  central 

1  Verworn,  loc.  cit.,  p.  42. 


96  BIOLOGICAL  LECTURES. 

capsule  died,  while  the  other  Radiolarian  which  had  lost  its 
nucleus  and  then  regained  it,  by  the  acquisition  of  a  central 
capsule  of  another  individual,  throve  well,  and  could  not  be 
distinguished  from  the  normal  Thalassicolla  in  the  first  vessel, 
upon  which  no  operation  had  been  performed. 

This  is,  in  my  judgment,  a  genuine  case  of  synthesis  of  a 
living  nucleated  cell,  by  bringing,  from  two  dissimilar  sources, 
the  cytoplasmic  and  nuclear  elements  together.  If  Stahl's  and 
Bonnier's  results,  on  the  synthesis  of  lichens  are  the  conclusive 
evidence  of  their  symbiotic  character,  may  not  the  Verworn's 
experiments  on  Thalassicolla  be  interpreted  as  equally  conclu- 
sive evidence  of  the  symbiotic  origin  of  the  nucleated  cell  .^ 
In  fact,  the  process  of  fecundation  is  nothing  more  than  a 
synthetic  production  of  one  nucleated  cell  from  two  nucleated 
cells  that  are  derived  from  independent  sources.  And,  further, 
there  is  good  ground,  as  the  phenomena  of  heredity  show,  for 
believing  that  each  germ  substance  retains  the  individual 
qualities  characteristic  of  its  origin,  throughout  all  stages  of 
later  development  of  the  organism. 

It  is  true  that,  in  the  case  of  a  lichen,  the  algal  and  the 
fungal  elements  may  exist  independently,  while  in  case  of  the 
nucleated  cell,  all  investigation  leads  to  the  conclusion  that 
when  the  nucleus  is  separated  permanently  from  the  cytoplasm 
or  the  cytoplasm  separated  from  the  nucleus,  they  invariably 
die,  sooner  or  later.^ 

This  is,  however,  no  objection  to  the  idea  of  the  symbiotic 
origin  of  the  nucleated  cell,  as  a  moment's  reflection  will 
show,  for  the  more  perfect  the  symbiotic  adaptation  of  two 
organisms,  the  greater  is  their  inability  to  live  independently, 
until  at  last  the  symbiotic  existence  between  the  two  organisms 
becomes  imperative,  if  they  are  to  continue  to  exist.     Remove 

1  For  recent  contributions  and  a  general  summary  of  our  knowledge  on  the 
relation  between  nucleus  and  cytoplasm,  see  O.  Ilertwig  :  Die  Zelle  und  die 
Gewebe,  Jena,  1893  '■>  E.  G.  Balbiani  :  N'ouvelles  recherches  experinientales  sur  la 
merotomie  des  infusoires  cilies.  Annales  de  micrographie,  Nos.  8,  9  and  10,  t.  IV, 
1892,  Paris;  Verworn  :  ■  Die  physiologische  Bedeiitufig  des  Zell kerns,  Bonn,  1891  ; 
Korschelt :  Beitrdge  zur  Morphologie  und  Physiologie  des  Zellkernes,  Jena,  1889  ; 
Whitman  :  The  Seat  of  Formative  and  Regenerative  Energy,  Journal  of  Mor- 
phology Vol.  II,    1888,  Boston. 


ON  THE  NATURE    OF  CELL-ORGANIZATION         97 

that  opportunity,  by  one  means  or  another,  of  their  combining 
thus  and  death  is  the  result,  somewhat  in  the  same  way  as  in 
the  case  of  an  obligatory  parasite,  which  though  descended 
from  a  free-living  ancestor,  dies  if  deprived  of  its  appropriate 
host. 

The  minute  organisms  which  we  assume  to  make  up  the 
cytoplasm  on  the  one  hand  and  nucleus  on  the  other,  probably 
once  were  free  and  lived  independently,  but  if  so,  it  is  plain 
they  have  since  lost  their  power  by  the  acquisition  of  sym- 
biotic habits.  By  adopting  symbiotic  habits,  however,  they 
acquired  the  ability  to  adapt  themselves  to  surroundings  so 
different  from  the  normal  habitat  of  each  that  neither  symbiont 
alone  could  have  lived  in  them,  and  thus  possibilities  each  was 
incapable  of  accomplishing  alone,  are  performed  successfully 
by  the  composite  organism.^  We  can  reasonably  suppose, 
therefore,  that  tJiose  cell- forming  organisms y  which  entered  into 
the  symbiotic  relation  in  the  past,  with  others,  have  survived  in 
a  modified  foj'in,  in  the  body  of  the  nucleated  cell,  while  those 
organisms  which  did  not,  have  perished  owing  to  their  ijiability 
to  adapt  themselves  to  the  vicissitudes  of  circumstances.  The 
nucleated  cell,  then,  is  a  colony  of  heterogeneous  organisms, 
which  maintains  a  complete  autonomy  and  behaves  as  if  it  were 
an  independent  organic  being,  subject  to  the  law  of  growth  and 
development  peculiar  to  itself. 

It  is  perhaps  needless  to  point  out,  after  we  have  dwelt  so 
much  on  the  subject,  that  the  fundamental  assumption  of  our 
theory  is  that  at  least  some  of  the  earliest  living  beings  that 
ever  existed  were  not  in  the  form  of  a  cell,  but  a  great  deal 
simpler,  somezvhat  like  those  individual  physiological  units 
whicJi  constitute  the  cytoplasm  and  the  nucleus  of  the  cell.  The 
cell  itself  was  formed  later  out  of  these  still  smaller  organisms 
which  already  existed.  It  is  not  our  purpose,  in  this  place,  to 
enter  into  an  extensive  examination  of  the  different  views  that 
have  been  brought  forward  to  explain  what  these  cell-forming 
units  are.  All  that  is  essential  for  our  present  purpose  is  the 
existence,  as  all  writers  unanimously  agree,  of  such  units  in 

1  See  important  remarks  on  the  result  of  commensalism  between  two  organisms. 
Sachs  :  Physiology  of  Plants,  pp.  391-394. 


98  BIOLOGICAL   LECTURES. 

the  cell,  each  with  the  power  of  assimilating,  of  growing  and 
of  multiplying  by  division.^ 

Perhaps  the  easiest  way  of  arriving  at  the  conception  of 
the  existence  of  such  ultra-microscopic  organisms  in  the  cell  is 
attained  by  separating  the  cytoplasm  from  the  nucleus  in  a 
given  cell,  say  an  Amoeba,  and  dividing  each  of  them  into 
smaller  and  smaller  pieces,  as  far  as  our  imagination  can  carry 
us.  *'  Just  as  in  division  of  the  chemical  mass  we  come  to  the 
chemical  molecule,  the  further  division  of  which  changes  the 
properties  of  the  substance,  so  in  the  continual  division  of  the 
Amoeba  we  should  come  to  a  stage  in  which  farther  division 
interfered  with  the  physiological  action ;  we  should  come  to  a 
physiological  unit,  corresponding  to,  but  greatly  more  complex 
than  the  chemical  molecule."  ^  Such  a  physiological  unit, 
Foster  suggests,  might  be  called  a  Somacide.  This  physiologi- 
cal unit  is  what  Weismann  calls  the  ''bearer  of  vitality,"  or 
Biopho7%  because  it  is  the  smallest  unit  which  exhibits  the 
primary  vital  forces.,  viz,  assiinila9ion  and  metabolism,  growtJi, 
and  multiplication  by  fission?  This  unit  is  not  the  chemical 
molecule,  hence  it  has  all  the  essential  characteristics  of  living 
organisms,  such  as  assimilation  and  division,  and  mere 
molecules  can  neither  assimilate  nor  multiply.  It  is,  in  fact, 
the  organism  itself,  with  all  fundamental  attributes  of  the 
higher  organism;  indeed,  the  reason  why  a  higher  organism 
exhibits  these  fundamental  properties,  is,  as  has  already  been 
mentioned,  because  its  component  units  are  endowed  with  such 
properties. 

Although  it  is  difficult  to  define  the  exact  nature  and  morpho- 
logical character  of  the  physiological  units  individually,  we  can 
study  them  collectively  in  the  phenomena  of  their  groiLpings. 

1  The  following  are  the  examples  of  names  recently  proposed  for  the  cell-form- 
ing units,  by  different  writers:  Bioblasts  (Altmann,  1887);  Pangenes  (Hugo  de 
Vries,  1889);  Somaades  (M.  Foster,  1888);  Plasomes  (J.  AViesner,  1892);  Biophors 
(Weismann,  1893);  Idioblasts  (O.  Hertwig,  1893).  Darwin's  Genunules,  Nageli's 
Micellcp,  Spencer's  Physiological  units,  Elsberg-Haeckel's  Plastidiiles,  Bechamp- 
Estor's  Microzymas  are  already  well  known,  It  is  important,  however,  to  bear  in 
mind  that  these  names  are  not  always  synonymous. 

2  M.  Foster:  A  Text-Book  of  Physiology,  5th  edition,  pp.  5-6. 
8  A.  Weismann:  The  Germ-plasma,  pp.  39-40. 


ON   THE   NATURE    OF  CELL-ORGANIZATION  99 

Take  chromosomes  of  the  nucleus,  for  example.  In  some  cells 
the  physiological  units  of  the  chromosome  arrange  themselves 
in  a  series  of  short  rods  —  chromatomeres  —  at  a  certain  period 
of  their  existence,  while  in  others  they  arrange  themselves  in 
a  series  of  elongated  filaments  at  the  corresponding  period. 
What,  therefore,  we  see  in  the  grouping  of  micro-organisms 
such  as  bacteria,  exactly  applies  to  those  units  which  form  the 
chromosomes.  As  De  Bary  ^  says  of  bacteria,  so  we  may  say 
here,  that  it  is  precisely  in  the  phenomena  of  grouping  that 
specific  peculiarities  of  conformation  of  such  physiological 
units  best  display  themselves,  being  collected  together,  as  it 
were,  in  large  quantity.  These  groupings  are  forms  of  vegeta- 
tive development,  growtJi-forms  of  the  minute  organism  which 
constitutes  the  physiological  unit  of  the  chromosome. 

The  growth-forms  of  the  physiological  unit  forming  the 
cytoplasm  of  the  cell  are  equally  characteristic,  as  is  plainly 
shown  in  the  reticular,  striated,  or  fibrillar  arrangements  of 
the. cytoplasm  in  different  kinds  of  cells. 

V. 

To  re-state  the  problem,  then,  we  may  say  that  there 
exist  two  easily  recognizable  elements  in  every  cell,  viz., 
{a)  the  nucleus,  or  more  strictly  the  chromosome,  and  {b) 
the  cytoplasm. 

It  has  been  conclusively  settled  by  a  number  of  investigators 
that  the  presence  of  both  is  essential  for  the  continued 
manifestation  of  life  activity  in  a  given  cell.  A  piece  of 
cytoplasm  or  nucleus  may  continue  to  maintain  a  certain  activity 
after  it  has  been  detached  from  the  cell,  but  it  perishes,  sooner 
or  later,  if  left  alone  by  itself. 

So  much  is  certain,  but  how  and  why  each  is  essential  to  the 
other  are  quite  other  questions,  and  have  received  different 
answers  from  different  investigators.  Some  claim  that  the 
nucleus  influences  the  cytoplasm  by  some  dynamical  action  ; 
others  hold  that  some  invisible  living  particles  of  the  nuclear 
matter  diffuse  through  the  nuclear  membrane,  and  become 
converted   into  the   substance  of  the  cytoplasm  ;    while   still 

1  De  r>ary  :  Lectures:  on  Bacteria,  Oxford.  1SS7. 


lOO  BIOLOGICAL   LECTURES. 

Others  believe  that  the  influence  of  the  nucleus  upon  the 
cytoplasm  is  that  of  a  fermentative  action.  To  a  fourth  group 
of  investigators,  {e.g.,  Verworn),  again,  the  action  of  nucleus 
and  of  cytoplasm  is  a  reciprocal  one,  the  nucleus  influencing 
the  cytoplasm,  and  the  cytoplasm  influencing  the  nucleus  in 
return,  by  the  interchange  of  the  metabolic  products.  This 
last  view  is  adopted  in  the  present  paper.  The  results  of 
operations  performed  on  the  nucleated  cell  seem  best  to 
support  this  view. 

All  of  these  explanations  are  finally  reduceable  to  two  funda- 
mentally different  views  one  may  take  in  regard  to  the  nature 
of  chromosome  and  cytoplasm  in  each  cell.  Some  hold  ia)  that 
the  nucleus  and  cytoplasm  are  essentially  one  and  the  same 
substance,  and  that  they  only  differ  from  each  other,  in  so 
far  as  their  stages  of  development  are  concerned.  Hence  the 
difference  between  the  nucleus  and  the  cytoplasm  is  merely 
that  of  degree.  Others,  on^he  other  hand,  maintain  ib)  that 
the  difference  between  the  nucleus  and  the  cytoplasm  is  not 
that  of  a  degree  of  development  of  one  and  the  same  substance, 
but  of  the  kind  of  material  of  which  each  is  composed. 

So  far  as  we  can  judge  from  the  micro-chemical  reactions 
of  nucleus  and  cytoplasm,  they  must  be  regarded  as  belonging 
to  two  substances  entirely  different  from  each  other.  There 
is  no  evidence  to  show  that  one  is  actually  produced  from  the 
other,  but  the  cytoplasm  always  originates  from  the  preced- 
ing cytoplasm,  and  the  nucleus  always  from  the  preceding 
nucleus. 

There  are,  then,  four  well  ascertained  facts,  in  regard  to 
the  nature  of  nucleus  and  cytoplasm  ;  viz., 

1.  The  two  elements  in  each  cell  —  the  chromosome  and 
the  cytoplasm  —  have  the  capacity  for  assimilation,  growth  and 
multiplication  by  division. 

2.  Each  is  essential  to  the  physiological  existence  of  the 
other. 

3.  The  chromosome  always  originates  from  the  preceding 
chromosome,  and  the  cytoplasm  from  the  preceding  cytoplasm. 

4.  Each  has  a  definite  micro-chemical  reaction,  different 
from  the  other,  and  is  composed  of  different  chemical  substance. 


ON   THE   NATURE    OF  CELL-ORGANIZATION  loi 

Any  theory  that  explains  the  nature  of  a  nucleated  cell 
must  explain  all  of  these,  and  hold  them  under  one  common 
point  of  view.  Such  a  theory  must,  in  short,  recognize  7iot  only 
the  profound  pJiysiological  interdcpeiidence  between  nucleus  and 
cytoplasm,  but  it  must  also  recognize  tJieir  nattcral  morphological 
independence. 

The  doctrine  of  symbiosis,  first  propounded  by  De  Bary,^ 
just  fulfils  these  requirements,  inasmuch  as  it  means  now,  in  a 
more  restricted  sense,  tJie  normal  fellowship  or  the  consortial 
union  of  two  or  more  organisms  of  dissimilar  origin,  each  of 
wJiicJi  acts  as  the  physiological  compliment  to  the  other  in  the 
struggle  for  existence. 

Under  the  assumption  of  such  a  principle  as  that  of 
mutualistic  symbiosis,  the  fact  of  natural  anatomical  difference 
between  the  chromosome  and  the  cytoplasm  can  only  be  har- 
monized with  the  fact  of  their  complimentary  physiological 
adaptation.  Only  on  the  assumption  that  the  chromosome  and 
cytoplasm  had  dissimilar  oi-igin,  can  we  understand  their 
constant  difference  in  optical,  microchemical  and  anatomical 
characters,  through  all  phases  of  their  activity. 

To  summarize  for  the  sake  of  clearness,  then,  the  general 
consequence  of  the  symbiotic  existence  to  its  participants,  we 
may  say,  that,  (i)  inasmuch  as  one  organic  being  comes  in 
connection  with  another  in  order  to  be  nourished  and  nourish 
the  other  in  return,  they  obtain  a  freedom  in  the  choice  of 
dwelling  place,  which  is  not  enjoyed  by  them  otherwise;  (2) 
symbiosis  of  twt)  dissimilar  organisms  induces  certain  modifi- 
cation in  each  symbiont,  by  the  suppression  of  certain 
characters  originally  present  in  each,  or  by  the  acquisition  of 
others,  which  were  formerly  absent;  (3)  when  the  adaptation 
of  one  symbiont  to  the  other  becomes  perfect,  the  whole 
community  behaves  like  a  new  organism,  subject  to  new  laws 
of  growth  and  of  development,  and  is  no  longer  subjected  to 
those  relating  to  each  symbiont  separately,  and  thus,  (4)  a 
power  of  adaptation  to  the  external  world  which  each  symbiont 
did  not  possess  individually,  in  the  struggle  for  existence,  may 
be  acquired  indirectly,  by  the  combined  efforts  of  the  two.    (5) 

^  De  l^ary  :  Die  Erscheiming  der  Symhiost\  Strassburg,  1S79. 


I02  BIOLOGICAL   LECTURES. 

In  proportion  as  the  symbiotic  adaptation  of  two  or  more 
organisms  becomes  more  and  more  perfect,  each  symbiont 
loses  the  power  of  living  independently  which  it  originally 
possessed. 

The  view  that  ascribes  a  symbiotic  significance  to  the 
association  of  these  two  different  kinds  of  cell-forming 
organisms  in  each  cell,  explains  the  following  points,  viz.,  (I) 
the  constant  difference  in  anatomical,  optical  and  micro-chemi- 
cal characteristics  between  the  chromosome  and  the  cytoplasm; 
(II)  the  maintenance  of  their  specific  identity  through  all 
phases  of  developviental  changes,  as  caryokinesis  and  fecunda- 
tion; (III)  the  participation  of  both  nucleus  and  cytoplasm  in 
the  manifestation  of  non-dcvelopmcntal  phenomena  of  cell- 
life,  such  as  secretion,  excretion,  etc. ;  (IV)  the  interchange  of 
metabolic  products  between  nucleus  and  cytoplasm  as  the 
necessary  outcome  of  a  symbiotic  mode  of  existence;  (V)  the 
reason  why  the  cytoplasm  separated  from  the  nucleus,  or  the 
nucleus  isolated  from  the  cytoplasm  invariably  perishes;  and, 
therefore,  (VI)  why  the  nucleus  and  cytoplasm  are  the  physio- 
logical organs  of  a  cell,  and  yet  they  are  not  organs  from  a 
morphological  or  developmental  standpoint. 

The  nuclear  substance  must  not  be  considered,  in  any  sense, 
as  inactive,  which  becomes  only  active  when  it  migrates  into 
the  cytoplasm  as  Hugo  de  Vries  ^  maintains  in  his  well-known 
work.  The  nuclear  substance  of  a  cell  is  just  as  much  active 
as  the  cytoplasm,  according  to  the  present  view,  but  in  an 
entirely  different  manner,  somewhat  in  the  same  way  as  the 
chlorophyll-bearing  algal  cells  and  the  colorless  fungal  elements 
in  a  lichen  are  active  at  the  same  time,  but  each  in  its  own  way. 

The  vital  properties  of  a  cell  do  not  reside  in  the  nucleus 
alone,  nor  in  the  cytoplasm  which  surrounds  it,  but  in  the  two 
together.  The  cell  maybe  destitute  of  a  cell-wall — cytotheca 
—  or  each  may  be  enclosed  within  its  own  cell-membrane,  or  a 
cell  may  exist  side  by  side  without  any  visible  boundary 
between  them  —  the  syncytium.  The  division  of  an  organism 
into  distinct  cell -entities  in  a  multicellular  organism  is  a 
phenomenon  widely  distributed,  it  is  true,  but  still  of  secondary 

1  Hugo  de  Vries:     Ijitracelhdare  Pangenesis^  Jena,  1889. 


ON   THE   NATURE    OF  CELL-ORGANIZATION.  1 03 

significance,^  due  to  physiological  causes,  I  believe,  emanating 
from  the  fundamental  difference  existing  between  the  chromo- 
some and  the  cytoplasm, — the  difference  between  the  two 
being  of  such  a  character  that  makes  their  mutual  association 
necessary  for  the  existence  of  each.  The  chromosome 
cannot  grow  beyond  a  certain  bulk,  nor  is  the  cytoplasm 
capable  of  unlimited  growth,  without  each  meeting  with 
restraining  influence  from  the  other,  if  one  may  express  it  in 
a  metaphorical  way.  The  formation  of  a  nucleated  cell  is, 
in  other  words,  a  secondary  adaptation  to  keep  the  nuclear  and 
cytoplasmic  material  within  the  reach  of  reciprocal  physiologi- 
cal influence  of  each.  The  division  of  the  cell,  when  such  exists, 
is  the  result  incidental  to  the  increase  in  the  number  of  two 
kinds  of  cell-forming  organisms  existing  in  each  nucleated  cell. 

The  sphere  within  which  the  symbiotic  reciprocal  influence  of 
these  two  cell-forming  organisms  is  felt,  corresponds  to  what 
Sachs  2  calls  the  eiiergid.  The  term  C7iergid  as  a  substitute  for 
the  modern  idea  of  the  nucleated  cell,  aptly  expresses  one 
aspect  of  the  cell-organism,  namely,  its  physiological  side. 
From  the  genetic  standpoint,  as  given  in  the  present  paper, 
this  single  energid  is  already  a  complex  of  at  least  two  kinds 
of  organisms,  different  in  their  anatomical  character,  in  their 
function,  and  in  their  origin. 

Stated  in  this  way,  the  view  is  not  a  new  one,  but  agrees,  in 
its  broadest  feature,  with  the  idea  of  a  cell  expressed  by 
Darwin  in  his  theory  of  Pangenesis,^  and  in  its  special  aspect 
which  considers  mutualistic  symbiosis  as  the  basis  of  cellular 
organization,  may  perhaps  add  a  more  concrete  meaning  to  his 
well-known  passage,  without  necessarily  adopting  his  further 
inference  from  it,  when  he  said  that  **an  orofanic  being:  is  a 
microcosm— a  little  universe,  formed  of  a  host  of  self-propa- 
gating organisms  inconceivably  minute  and  numerous  as  the 
stars  in  the  heavens." 

1  Sachs:  Lectures  on  the  Physiology  of  Plants,  p.  "jt^. 

2  Julius  V.  Sachs:  Physiologische  Notizen  II.  Beitrdge  zur  Zellentheorie.  Flora: 
Jahrg.  75,  1892.  Reprinted  in  his  Gesamnielte  Abhandlungen,  11.^  1893,  pp.  1 1  so- 
il 55- 

®  Darwin:  Proz'isional  Hypothesis  of  Pangenesis  {Animals  and  Plants  under 
Domestication,  vol.  ii.);    The  Descent  of  Man,  Appleton,  p.  22S. 


SIXTH     LECTURE. 


THE    INADE:QUACY    of    the    CELL-THEORY    OF 
DEVELOPMENT.! 

C.  O.  WHITMAN. 

The  doctrine  of  Schleiden  and  Schwann  that  in  cell-formation 
lies  the  whole  secret  of  organic  development,  has  held  the  place 
of  a  central  axiom  in  biological  work  and  speculation  for  over 
half  a  century.  All  this  time  the  cell  has  been,  as  it  were,  the 
alpha  and  omega  of  both  morphological  and  physiological 
research.  Regarded  as  a  primary  element  of  structure,  it  has 
come  to  signify  in  the  organic  world  what  the  atom  and  mole- 
cule signify  in  the  physical  world. 

The  traditional  cell-staitdpoint  has  been  most  exactly  defined 
by  Schleiden  and  Schwann.  In  his  celebrated  ''  Beitrage  zur 
Phytogenesis "  (Miiller's  Archiv,  1838),  Schleiden  sets  forth 
the  cell-doctrine,  which  he  limited  to  plants,  in  the  following 
words  :  ''Each  cell  leads  a  dojible  life ;  an  independent  07ie, 
pertaining  to  its  oivn  development  alojte ;  and  a?iot/ier  inci- 
dental, in  so  far  as  it  has  become  an  integral  part  of  a  plant '^ 

Schwann,  in  his  classical  Researches  of  1839,  extends  the 
same  view  to  the  entire  organic  world. 

''Each  cell,''  he  affirms,  "is,  witJiin  certain  limits,  an  individ- 
ual, an  independent  zuhole.  The  vital  phefiomena  of  one  are 
repeated,  entirely  or  in  part,  in  all  the  rest.  These  individuals, 
however,  are  not  ranged  side  by  side  as  a  mere  aggregate,  but 
so  operate  together,  in  a  manner  imknown  to  ns,  as  to  prodtice 
an  Jiarmonious  ivJiole''     (Introduction,  p.  2.) 

"  The  whole  organism  subsists  only  by  means  of  the  recipro- 
cal action  of  the  single  elementary  parts!' 

The  method  of  reasoning  is  precisely  the  same  as  we  have 
seen  in  some  of  the  latest  experimental  studies  on  cleavage. 
Witness    the    following  :     "  If    we    find    that    some    of    these 

1  Read  Aug.  31,  at  the  Zoological  Congress  of  the  World's  rolumbian  Kxposition. 


I06  BIOLOGICAL   LECTURES. 

elementary  parts,  not  differing  from  the  others,  are  capable  of 
separating  themselves  from  the  organism,  and  pursuing  an 
independent  growth,  we  may  thence  conclude  that  each  of  the 
other  elementary  parts,  each  cell,  is  already  possessed  of  power 
to  take  up  fresh  molecules  and  grow  ;  and  that,  therefore, 
every  elementary  part  possesses  a  power  of  its  ozvn,  aji  inde- 
pendent life,  by  means  of  ivhich  it  would  be  enabled  to  develop 
independently,  if  the  relations  which  it  bore  to  external 

PARTS    were    but    SIMILAR    TO    THOSE     IN    WHICH    IT    STANDS    IN 

THE  ORGANISM.  The  ova  of  animals  afford  us  examples  of 
such  independent  cells,  growing  apart  from  the  organism." 
{I.e.  p.  192). 

In  these  words  of  Schleiden  and  Schwann  we  see  no  vague 
anticipation,  but  a  clear  statement,  of  the  cell-standpoint  of 
to-day.  The  organism  consists,  morphologically,  of  cells,  and 
subsists,  physiologically,  by  means  of  the  "reciprocal  action" 
of  the  cells.  Organizatioji  means  cellular  structure,  and 
ontogeny  means  cell-formationib  '^  Der  gleiche  Elementarorganis- 
mus  ist  es,  der  Thiere  nnd Pflanzen  znsammensetzt.''   (Schwann.) 

In  this  ''double  life,"  this  ''harmonious  whole,"  this  "recip- 
rocal action"  of  "elementary  organisms,"  this  "operating 
together  in  an  unknown  manner,"  we  see  the  "cell-state" 
theory,  the  "unknown  principle  of  correlation,"  the  "correlative 
differentiation,"  the  "cellular  interaction  "  of  current  literature. 

Much  as  we  have  enlarged  our  knowledge  of  the  cell,  we 
are  still  looking  at  the  problems  of  life  from  the  point  of 
view  occupied  by  the  founder  of  the  cell-doctrine.  The  most 
notable  advances  in  cytology  have  but  tended  to  define  and 
emphasize  the  cell-standpoint.  The  discovery  that  all  cells 
arise  by  division  of  preexisting  cells,  neatly  embodied  in  Vir- 
chow's  maxim,  ^^ omnis  cellula  e  cellnla'' ;  the  extension  and 
verification  of  this  maxim  furnished  by  Gegenbaur  in  1861, 
in  demonstrating  tJie  vertebrate  egg  to  be  a  single  cell ;  and  the 
proof  obtained  during  the  last  twenty  years  that  the  internal 
processes  of  cell-division  are  fimdamentally  the  same  in  both 
plants  and  animals,  —  all  these  capital  steps  forward  have 
tended  to  magnify  the  importance  of  the  cell  as  a  universal 
unit  of  structure. 


THE  INADEQUACY  OF  THE   CELL-THEORY.       lOJ 

All  higher  organization  is  supposed  to  begin  with  cell-forma- 
tion, and  to  reach  its  fullest  expression  in  the  mutuality  of  the 
constituent  cells.  Whether  the  cytoplasm  be  regarded  as 
isotropic  or  as  definitely  organized,  whether  the  hereditary 
substance  be  identified  with  the  egg  as  a  whole,  or  with  the 
nuclear  chromosomes  alone,  the  cell-dogma  is  still  supreme. 

Our  microscopes  resolve  the  organism  into  cells,  and  onto- 
geny shows  that  the  many  cells  arise  from  one  cell  ;  hence, 
the  organism  seems  to  be  the  product  of  cell-formation,  and 
the  cleavage  of  the  germ  seems  to  be  a  bicilding  process. 
The  cell-theory  points  us  to  very  definite  units,  as  the  ele- 
ments of  organization,  and  thus  offers  what  has  for  a  long  time 
appeared  to  be  a  rational  basis  for  the  investigation  of  life- 
phenomena.  All  the  search-lights  of  the  biological  sciences 
have  been  turned  upon  the  cell  ;  it  has  been  hunted  up  and 
down  through  every  grade  of  organization  ;  it  has  been 
searched  inside  and  out,  experimented  upon,  and  studied  in  its 
manifold  relations  as  a  i^nit  of  form  and  function.  It  has  been 
taken  as  the  key  to  ontogeny  and  phylogeny,  and  on  it  theories 
of  heredity  and  variation  have  been  built.  For  a  long  time  it 
has  been  regarded  as  a  decisive  test  of  homology  in  germ- 
layers,  tissues,  and  organs.  Fundamental  distinctions  have 
been  made  between  ////r^^-cellular  and  mter-ce\\u]d.r  organiza- 
tion, between  unicellular  and  multicellular  organisms  and 
organs,  between  cellular  and  acellular  growth  and  develop- 
ment, between  the  processes  of  fission  and  regeneration  in  the 
protozoan  and  the  metazoan,  between  differentiation  witJiin 
the  cell  and  dmoiig  cells,  between  the  formative  forces  which 
shape  the  infusorian  and  those  which  act  in  a  many-celled 
organism. 

An  organism  of  many  cells  is  supposed  to  differ  from  one  of 
one  cell,  somewhat  as  a  complex  molecule  differs  from  a  simple 
one.  The  complex  unit  bears  not  only  the  structure  of  its  in- 
dividual parts,  but  also  a  totally  new  structure  formed  by  the 
union  of  these  parts.  In  like  manner  the  organism  is  fancied 
to  carry  at  least  two  distinct  organizations,  the  organization  of 
the  separate  cells  and  that  of  the  cells  united.  The  higher 
organization  thus  differs,  qualitatively,  from  the  lower,  so  that 


I08  BIOLOGICAL   LECTURES. 

we  may  have  analogies,  but  no  homology  of  organs  between 
unicellular  and  multicellular  organisms. 

How  sharply  the  line  is  drawn  in  this  regard  is  shown  in 
the  scrupulous  care  with  which  authors  avoid  the  suggestion 
of  anything  comparable  to  muscle  or  nerve  in  the  infusorian. 
The  Ehrenberg  view  of  infusorian  organization  demanded 
altogether  too  much,  and  we  have  swung  to  the  opposite 
extreme  of  thinking  that  the  very  idea  of  such  comparison  is 
forbidden  by  the  cell-doctrine.  Any  suggestion  of  a  possible 
community  of  origin  between  an  organ  —  say  the  viouth  —  of 
such  an  animal  and  the  corresponding  structure  of  a  cellular 
organism,  would  be  quickly  relegated  to  the  livibiis  fatiiorum. 
Who  dares  question  the  proposition  that  there  can  be  no 
morphological  identity  between  an  organ  formed  without  cells 
and  one  formed  with  cells  t  No  matter  how  complete  the 
physiological  correspondence,  the  two  things  must  be  assumed 
to  differ  toto  coelo,  as  mcc^ured  by  the  cell-rule.  That  is  the 
cell-standpoint. 

While  the  cell-doctrine  has  been  carried  steadily  forward, 
confidence  in  its  all-sufficiency  has  been  somewhat  shaken  from 
time  to  time,  and  a  few  cautious  protests  have  been  ventured 
against  the  complete  ascendancy  of  the  cell  as  a  unit  of  organ- 
ization. Botanists,  among  whom  in  this  particular  the  name 
of  Sachs  stands  foremost,  have  led  the  way  to  another  stand- 
point, which,  in  contradistinction  to  the  prevailing  one,  may 
be  called  the  o^'ganism-standpoifit.  Among  zoologists,  Rauber 
has  most  boldly  and  ably  defended  this  point  of  view;  and 
more  recently  Wilson  has  expressed  similar  views,  but  with 
reservations  that  still  uphold  the  cell-standpoint.  Driesch, 
too,  obtains  experimental  proof  that  "  the  mode  of  cleavage  is 
something  unessential  to  the  future  animal,"  but  still  he  feels 
compelled  to  explain  the  organism  from  the  cell-standpoint,  — 
that  is,  he  supposes  that  the  organism  is  determined  by 
correlative  differentiation  of  homodynamous  ("omnipotent") 
cells  or  nuclei.  The  position  is  altogether  similar  to  that  of 
Oscar  Hertwig  and  Wilson.  Wilson,  however,  holds  that  the 
cleavage  may  secondarily  acquire  a  "mosaic"  significance,  and 
herein   makes   a  decided   advance  towards   a  pre-organization 


THE  INADEQUACY  OF   THE   CELL-THEORY.       109 

theory.  A  certain  grade  of  organization  as  the  result  of 
heredity  rather  than  of  cleavage  is  conceded  for  annelid 
development,  and  for  all  forms,  in  so  far  as  future  characters 
are  foreshadowed  in  cleavage  stages.  This  is  a  limited  appli- 
cation of  the  view  which  I  believe  holds  true  of  all  eggs,  even 
before  cleavage  begins.  It  will  be  easy  to  show  that  the  very 
facts  generally  relied  upon  to  disprove  the  existence  of  organi- 
zation in  the  G.gg  furnish  very  strong  evidence  in  support  of  it. 

The  question  as  to  the  presence  of  organization  is  not  set- 
tled by  the  form  of  cleavage.  Eggs  that  admit  of  complete 
orientation  at  the  first  or  second  cleavage,  or  even  before  cleav- 
age begins,  are  commonly  supposed  to  reflect  precociously 
the  later  organization,  while  eggs,  in  which  such  early  orien- 
tation is  impossible,  are  supposed  to  be  more  or  less  completely 
isotropic  and  destitute  of  organization.  When  the  region  of 
apical  growth  is  represented  by  conspicuous  teloblasts,  the 
fate  of  which  is  seen  to  be  definitely  fixed  from  the  moment  of 
their  appearance,  we  find  it  impossible  to  doubt  the  evidence 
of  organization,  or  **  precocious  differentiation,"  as  it  is  con- 
ventionally called.  When  the  same  region  is  composed  of 
more  numerous  cells,  among  which  we  are  unable  to  distin- 
guish special  proliferating  cells,  we  lapse  into  the  irrational 
conviction  that  the  absence  of  definitely  orientable  cells  means 
just  so  much  less  organization. 

Cell-orientation  may  enable  us  to  infer  organization,  but  to 
regard  it  as  a  measure  of  organization  is  a  serious  error.  The 
organization  of  a  vertebrate  embryo  cannot  be  said  to  be 
less  advanced  than  that  of  an  annelid  embryo,  because  it 
lacks  the  unicellular  teloblasts  which  the  latter  may  possess. 
The  regular  holoblastic  cleavage  of  the  mammalian  ^gg  is 
evidently  no  index  to  its  grade  of  organization.  The  more 
carefully  we  compare  the  cleavage  in  different  eggs,  the  more 
clear  it  becomes  that  the  test  of  organization  in  the  ^gg  does 
not  lie  in  its  mode  of  cleavage,  but  in  subtile  formative  pro- 
cesses. We  find  the  most  unlike  forms  of  cleavage  issuing  in 
the  same  remarkable  form-phases  ;  for  example,  the  primitive 
streak  of  mammalian  and  avian  eggs  ;  and  conversely,  we  find 
identical  forms  of  cleavage  leading  to  fundamentally  different 


no  BIOLOGICAL   LECTURES. 

results  ;  for  example,  in  the  ^gg  of  the  polyclad  as  compared 
with  that  of  the  mollusc  or  the  annelid,  where  ''  cells  having 
precisely  the  same  origin  in  the  cleavage,  occupying  the  same 
position  in  the  embryo,  and  placed  tinder  the  same  mechanical 
conditions,  may  nevertheless  differ  fundamentally  in  morpJio- 
logical  significance. ' '      (Wilson .) 

The  most  remarkable  feature  of  avian  development  is  the 
primitive  streak.  The  presence  of  this  feature  in  typical  form, 
in  such  an  ^gg  as  that  of  the  mammal,  is  certainly  one  of  the 
most  significant  facts  in  embryology.  The  conclusion  is  here 
forced  upon  us  —  and  I  see  no  escape  from  it  —  that  the  forma- 
tion of  the  embryo  is  not  controlled  by  the  form  of  cleavage. 
The  plastic  forces  heed  no  cell-boundaries,  but  mould  the 
germ-mass  regardless  of  the  way  it  is  cut  up  into  cells.  That 
the  forms  assumed  by  the  embryo  in  successive  stages  are  not 
dependent  on  cell-divisio#,  may  be  demonstrated  in  almost  any 
Ggg-  Watch  the  expansion  of  the  blastoderm  in  the  pelagic 
teleost  ^gg,  the  formation  of  the  germ-ring,  and  especially 
the  axial  concentration  of  material,  which  is  so  beautifully 
illustrated  in  these  eggs.  Such  developmental  processes 
are,  if  I  mistake  not,  clearly  indicative  of  some  sort  of  organ- 
ization. 

The  formation  of  the  whole  from  a  part,  regarded  by  some 
as  conclusive  evidence  of  isotropy  and  correlative  tv/Z-differenti- 
ation,  no  more  disproves  the  existence  of  definite  organization 
in  the  case  of  the  ^gg  than  in  the  case  of  hydra.  A  fragment 
of  a  hydra  may  reproduce  the  whole  organism  ;  and  in  so  doing 
act  as  a  unit,  not  as  a  fraction  of  a  unit.  In  the  same  way, 
one  of  the  first  two  or  four  blastomeres,  when  severed  from 
vital  connection  with  its  fellow  or  fellows,  may  develop  as  a 
unit,  not  as  a  half-unit,  precisely  as  Wilson  insists  is  the  case 
in  Amphioxus. 

If  the  isolated  blastomere  continues  for  a  while  to  form  cells 
as  if  it  were  a  half-unit  or  a  quarter-unit,  and  only  later  mani- 
fests the  whole  unit-power  of  the  organism,  I  see  no  reason  to 
conclude  that  the  case  is  fundamentally  different.  In  either 
case  the  part  has  the  power  of  reorganizing  itself  into  the 
whole,  and  it  makes  no  essential  difference  whether  the  reor- 


THE  INADEQUACY  OF   THE   CELL-THEORY.       I  I  I 

ganization  be  accomplished  at  once,  before  cells  are  formed,  or 
gradually,  while  cell-formation  is  going  on. 

If  we  no  longer  hesitate  to  accept  Briicke's  view  that  the 
functions  of  the  cell  are  proof  of  organization,  although  our 
best  microscopes  fail  to  give  us  any  idea  of  what  it  consists  in, 
it  certainly  ought  not  to  be  difficult  to  regard  the  Qgg  as  a 
young  organism,  and  the  developmental  phenomena  as  proof  of 
organization.  Such  organization  is,  in  fact,  conceded  when  we 
speak  of  the  Qgg  as  the  rudiment  of  an  organism  (''Anlage 
eines  Organismus,"  O.  Hertwig),  but,  nevertheless,  we  go  on 
insisting  that  cellular  structure  is  the  essence  of  a  higher 
organization. 

We  are  so  captured  with  the  personality  of  the  cell  that  we 
habitually  draw  a  boundary-line  around  it,  and  question  the 
testimony  of  our  microscopes  when  we  fail  to  find  such  an 
indication  of  isolation.  We  have  so  long  insisted  on  these 
boundary-lines  as  limiting  homologies  that  we  find  it  extremely 
difficult  to  ignore  them.  How  difficult  it  is,  for  example  to 
regard  a  multicellular  nephridial  funnel  as  the  exact  homologue 
of  the  unicellular  funnel.  If  the  organ  consist  of  one  cell,  the 
tube  is  intm-cQ\\\\\2iY  ;  if  of  many  cells,  then  it  is  inUr-cel\u\3.T. 
But  we  have  the  ''tube"  and  the  ''flame"  just  as  perfect  with 
one  cell  as  with  many,  as  Vejdovsky's  studies  make  very 
certain.  How  idle,  then,  to  deny  homology  between  two 
such  organs  merely  because  one  is  hi/ra-  and  the  other  iuUr- 
cellular.  And  yet  that  is  precisely  what  we  have  been  accus- 
tomed to  do. 

Now  this  one  case  illustrates,  as  I  believe,  a  general  truth  of 
no  little  importance.  T/ie  nepJirostome  is  a  nephrostoine  all  the 
same  zvhethc}^  it  consist  of  one  cell,  tzvo  cells,  or  many  cells.  Its 
form  and  fnnction  are  both  independent  of  the  number  of  com- 
ponent cells.  Cells  multiply,  but  the  organ  retnains  the  same 
throughout.  So  far  as  homology  is  concerned,  the  existence  of 
cells  may  be  ignored. 

May  we  not  go  further,  and  say  that  an  organism  is  an  organ- 
ism from  the  oigg  onward,  quite  independently  of  the  number 
of  cells  present  "i  In  that  case  continuity  of  organization  would 
be  the  essential  thing,  while  division  into  cell-territories  might 


112  BIOLOGICAL  LECTURES. 

be  a  matter  of  quite  secondary  importance.  As  the  nephro- 
stome  is  not  the  result  of  cell-formation,  but  exists  as  such 
before  division  into  cells,  so  the  organism  exists  before  cleavage 
sets  in,  and  persists  throughout  every  stage  of  cell-multipli- 
cation. Continuity  of  organization  does  not  of  course  mean 
preformed  organs,  it  means  only  that  a  definite  structural 
foundation  must  be  taken  as  the  starting-point  of  each  organ- 
ism, and  that  the  organism  is  not  multiplied  by  cell-division, 
but  rather  continued  as  an  individuality  through  all  stages  of 
transformation  and  sub-division  into  cells. 

We  have  long  been  aware  that  the  cell  could  not  be  taken  as 
the  ultimate  unit  of  life,  and  every  notable  effort  to  account  for 
heredity  has  led  to  the  postulation  of  primary  elements  in  com- 
parison with  which  tht^  cells  appear  as  complex  organisms. 
Since  Ernst  Briicke  first  contended  for  the  organization  of  the 
cell  in  1861,  and  the  existence  of  "smallest  parts"  as  the  basis 
of  this  organization,  we  have  seen  similar  ideas  reappear  in  the 
''physiological  units"  of  Herbert  Spencer,  the  ''gemmules"  of 
Darwin,  the  ''micellae  "  of  Nageli,  the  "plastidules  "  of  Elsberg 
and  Haeckel,  the  "  inotagmata  "  of  Th.  Engelmann,  the  "pan- 
gens"  of  de  Vries,  the  "plasomes"  of  Wiesner,  the  "idioblasts" 
of  Oscar  Hertwig,  and  the  "biophores"  of  Weismann. 

After  the  discovery  of  cell-division  as  the  law  of  cell-forma- 
tion, and  after  the  scheme  of  the  cell  set  up  by  Schleiden  and 
Schwann  had  been  revised  and  reduced  to  essentialities  by 
Leydig,  Max  Schultze,  and  others,  the  next  great  step  forward 
in  the  cell-doctrine  must  be  credited  to  Briicke,  who,  seeing  that 
the  phenomena  of  life  could  not  be  referred  to  a  striictiu'clcss 
substance,  declared  for  the  orga7ii::;atio7i  of  the  cell  in  words 
that  were  scarcely  less  than  revolutionary. 

"  We  must  therefore,"  says  Briicke,  ascribe  to  living  cells,  in  addi- 
tion to  the  molecular  structure  of  the  organic  compounds  which  they 
contain,  still  another,  and  otherwise  complicated,  structure  ;  and  this 
it  is  that  we  designate  by  the  name  organization." 

Further,  in  his  own  words  :  "  Wir  miissen  in  dcr  Zelle  imtner  cinen 
kleinen  Thierleib  se/ien,  und  diirfen  die  Analogicn^  ivelche  zivischeji  ihr 
und  den  kleinsten  Thierforine?i  exisfiren^  niemals  aus  de7i  Augen  lassen^ 
(Elementarorganismen,  p.  387.) 


THE  INADEQUACY  OF  THE   CELL-THEORY.       II3 

On  the  botanical  side,  Sachs  has  maintained  since  1865  ("  Experi- 
mental-Physiologie ")  that  protoplasm  is  an  ^''organized  body^'  {cf. 
Lectures  on  Physiology,  1887,  p.  206-7).  While  Briicke  contended 
for  organization  7vithin  the  cell,  and  remained  true  to  the  cell-theory 
of  all  higher  organization,  Sachs,  Goebel  and  some  other  botanists 
early  challenged  the  doctrine  of  cell-hegemony.  Sachs  briefly  indi- 
cates his  standpoint  in  the  following  words  : 

"  To  many,  the  cell  is  always  an  independent  living  being,  which 
sometimes  exists  for  itself  alone,  and  sometimes  'becomes  joined  with ' 
others  —  millions  of  its  like,  in  order  to  form  a  cell-colony,  or,  as 
Haeckel  has  named  it  for  the  plant  particularly,  a  cell-republic.  To 
others  again,  to  whom  the  author  of  this  book  also  belongs,  cell- 
formation  is  a  phenomenon  very  general,  it  is  true,  in  organic  life,  but 
still  only  of  secondary  signijicance :  at  all  events,  it  is  merely  one  of 
the  numerous  expressions  of  the  formative  forces  which  reside  in  all 
matter,  in  the  highest  degree,  however,  in  organic  substance."  (Lect- 
ures, etc.,  p.  73.) 

Briicke's  great  merit  consists  in  this,  that  he  taught  us  the 
necessity  of  assuming  stnicture  as  the  basis  of  vital  phenomena, 
in  spite  of  the  negative  testimony  of  our  imperfect  microscopes. 
That  function  presupposes  structure  is  now  an  accepted  axiom, 
and  we  need  only  extend  Briicke's  method  of  reasoning,  from 
the  tissue-cell  to  the  egg-cell,  in  order  to  see  that  there  is  no 
escape  from  the  conclusion  that  the  whole  course  of  develop- 
mental jDhenomena  must  be  referred  to  organization  of  some 
sort.  DevclopDicnt,  no  less  tJian  other  vital  p/ie?iomefta,  is  a 
function  of  organi::ation. 

Nageli  followed  the  same  method  of  reasoning  when  he  con- 
cluded that  the  organism  was,  in  a  certain  sense,  *' vorgebildet " 
in  the  germ-cell  (Beitrage  zur  wiss.  Botanik,  Heft  IL  i860). 
This  point  of  view  is  well  expressed  in  his  classical  work,  the 
*'  Theorie  der  Abstammungslehre,"  where  he  says:  *'  Organisms 
differ  from  one  another  as  egg-cells  no  less  than  in  the  adult 
state.  The  species  is  contained  in  the  ^gg  of  the  hen  as  com- 
pletely as  in  the  hen,  and  the  hen's  egg  differs  from  the  frog's 
^gg  just  as  widely  as  the  hen  from  the  frog." 

While  all  will  admit  that  the  organization  of  the  ^gg  is  such 
as  to  predetermine  the  organism,  few  will  be  prepared  to  admit 
that    tJie  adult  onraiiization  is  identical   in  its  individuality 


114  BIOLOGICAL    LECTURES. 

with  that  of  the  egg.  The  organism  is  regarded  rather  as  a 
community  of  such  individualities,  bound  together  by  inter- 
action and  mutual  dependence.  According  to  this  view,  de- 
velopment does  not  consist  in  carrying  forward  continuous 
changes  in  the  same  individual  organization,  but  in  multiplying 
individualities,  the  complex  of  which  represents,  at  every 
stage,  not  tJie  organism,  but  one  of  an  ascending  series  of 
organisms,  which  is  to  terminate  in  the  adult  form. 

In  the  egg-cell  we  are  supposed  to  have  an  elementary  organ- 
ism ;  in  the  two-cell  stage,  two  elementary  organisms,  forming 
together  an  organism  of  a  totally  different  order,  based  on 
a  new  scheme  of  organization.  In  the  four-cell  stage  we 
have  another  organism,  in  the  eight-cell  stage  another,  and 
so  on. 

**  Physiological  division  of  labor,"  as  Milne-Edwards  first 
phrased  it,  is  unquestionably  a  principle  of  wide  application. 
Given  the  cells  as  morphological  units  and  this  physiological 
principle,  the  evolution  of  a  cellular  organism,  may  be  con- 
ceived of  as  a  most  simple  affair.  From  a  simple  colony  of 
like  cells,  we  pass  to  a  commonwealth  of  differentiated  and 
mutually  dependent  cells.  A  multitude  of  independent  cell- 
organisms,  adopting  mutual  service  as  the  best  economy,  find 
themselves  in  the  end  incapable  of  independent  life,  and  so 
firmly  bound  together  in  interdependence,  that  they  constitute 
a  complex  individual.  The  usual  conception  of  this  division 
of  labor  is,  as  Herbert  Spencer  ^  has  recently  stated  it,  '*  an 
excJiaiige  of  services,  — -^w  arrangement  under  which,  while  one 
part  devotes  itself  to  one  kind  of  action,  and  yields  benefits  to 
all  the  rest,  all  the  rest,  jointly  and  severally  performing  their 
special  actions,  yield  benefits  to  it  in  exchange.  Otherwise 
described,  it  is  a  system  of  mutual  dependence." 

We  habitually  apply  this  anthropomorphic  conception  to 
every  grade  of  organization.  The  higher  organism  is  regarded 
as  a  colony  of  cells  ;  the  cell  as  a  colony  of  simpler  units, 
nucleus,  centrosome,  and  so  on  ;  the  nucleus  as  a  colony  of 
chromosomes ;  the  chromosome,  according  to  Weismann's  ter- 
minology,  as   a   colony  of   "ids";    the    ''id"    as   a  colony  of 

1  The  Contemporary  Review,  February,  March,  and  May,  1893. 


THE  INADEQUACY  OE   THE   CELL-THEORY.       I  15 

"determinants";  the  ''determinant"  as  a  colony  of  "  bio- 
phores,"  and  the  ''biophore"  as  a  colony  of  molecules. 

In  proportion  as  division  of  labor  is  carried  out,  inter- 
dependence is  increased,  and  the  units  become  more  and  more 
intimately  associated.  The  struggle  for  existence  is  supposed 
to  extend  to  the  cells,  and  even  to  the  biophores.  Symbiotic 
relations  are  fought  out,  refined,  and  confirmed  by  natural 
selection,  and  eventually  reduced  to  a  system  of  mutual  adap- 
tations which  are  fancied  to  be  the  basis  of  organic  unity. 
'  Whether  organization  is  wholly  a  matter  of  acquisition,  and 
whether  it  became  possible  only  as  a  result  of  symbiotic  ad- 
vantages accidentally  discovered  in  the  struggle  for  existence, 
need  not  here  be  discussed.  It  is  enough  for  present  purposes 
to  know  that  organization  exists,  and  that  organic  unity 
depends  on  intrinsic  properties  no  less  than  does  molecular 
unity. 

It  is  not  division  of  labor  and  mutual  dependence  that 
control  the  union  of  the  blastomeres.  It  is  neither  functional 
economy  nor  social  instinct  that  binds  the  two  halves  of  an  ^g'g 
together,  but  the  constitutional  bond  of  individual  oi'ganisa- 
tion.  It  is  not  simple  adhesion  of  independent  cells,  but 
integral  structural  cohesion. 

,  That  organization  precedes  cell-formation  and  regulates  it, 
rather  than  the  reverse,  is  a  conclusion  that  forces  itself  upon 
us  from  many  sides.  In  the  infusoria  we  see  most  complex 
organizations  worked  out  within  the  limits  of  a  single  cell. 
We  often  see  the  formative  forces  at  work  and  structural 
features  established  before  fission  is  accomplished.  Cell- 
division  is  here  plainly  the  result,  not  the  cause,  of  structural 
duplication.  The  multicellular  Microstoma  behaves  essentially 
in  the  same  way  as  the  unicellular  Stentor,  or  the  multinucleate 
Opalinopsis  of  Sepia.  The  Microstoma  organization  duplicates 
itself,  and  fission  follows.  The  chain  of  buds  thus  formed 
bears  a  most,  striking  resemblance  to  that  of  Opalinopsis,  and 
the  resemblance  must  lie  deeper  in  the  organization  than  cell- 
boundaries. 

Compare  the  results  obtained  by  artificial  division  in  two 
such  forms  as  Stentor  and  Hydra.     The  two  courses  of  regen- 


ii6 


BIOLOGICAL   LECTURES. 


eratioR  are  so  exactly  parallel  that  one  cannot  fail  to  see  at 
once  that  the  formative  forces  operate  in  essentially  the  same 
manner  with  the  one-celled  as  with  the  many-celled  organism. 
Gruber's  experiment,  as  described  in  his  recent  article,  '^Micro- 
scopic Vivisection''  (Berichte  der  Naturforschenden  Gesellschaft 
zu  Freiburg,  Vol.  VII,  Part  i,  1893),  illustrates  well  this  point. 
A  Stentor  was  cut  into  three  pieces.  A,  B,  C,  each  of  which 
regenerated  the  missing  parts  within  24  hours.     The  anterior 


M\ 

m 

A ' 

m\ 

vc 


Fig.  I.  —  Regeneration  of  a  vStentor  cut  into  three  parts,  A,  B,  C.     tr  ==  pulsating 
vacuole.     S  =  regenerating  frontal  field. 

end  regenerated  posterior  end,  and  vice  versa.  The  middle 
piece  regenerated  both  ends  —  the  complicated  frontal  field 
with  its  mouth,  pharynx,  long  cilia,  pulsating  vesicle,  etc.,  as 
well  as  the  simpler  posterior  region. 

Treat  a  Hydra  in  the  same  way  and  similar  results  will  follow. 
In  both  cases  the  orientation  of  the  parts  will  remain  the  same 
as  that  of  the  whole.  Gruber  repeated  the  division  of  Stentor 
four   times   in   succession,    getting   perfect   regeneration   each 


THE  INADEQUACY  OF  THE   CELL-THEORY.       117 

time,  but  smaller  individuals,  as  no  growth  was  possible. 
The  experiment  reminds  one  of  the  half-  or  quarter-sized 
embryos  obtained  by  separating  the  first  two  or  four  blasto- 
meres. 

Gruber's  highly  interesting  paper  calls  attention  to  the  iden- 
tity in  form  and  structural  detail  of  the  ''membranellae  "  of 
Stentor  with  the  so-called  '*  corner-cells  "  (Eckzellen)  of  mol- 
luscs {Cyclas  cornea).  The  comparison  is  a  most  instructive 
one,  illustrating  in  the  most  conclusive  manner  that  differenti- 
ation of  the  parts  of  the  soma  depends,  not  on  the  interaction 
of  cells,  but  upon  the  elementary  structure  of  the  protoplasm. 


Fig.  2.  —  A,  three  membranellae  of  Stentor,  B,  membranella  in  section. 
C  Section  at  the  base  of  the  two  plates.  Bl,  Basal  lamella.  Ef,  Terminal  fibre. 
Bf,  l>asal  fibril.     A',  Nucleus. 


The  membranellae  of  the  frontal  field  of  Stentor  consist  of  two 
thin,  adherent  plates,  each  of  which  represents  a  number  of 
coalesced  cilia.  The  structure  has  a  basal  seam  or  ridge  ^ 
(Leiste),  and  a  basal  lamella  which  is  continued  into  a  termi- 
nal fibre.  All  these  fibres  are  connected  by  the  basal  fibril, 
through  which  the  movements  of  the  membranellae  are  evi- 
dently regulated. 

Now  this  highly  differentiated  organ,  the  membranella,  is 
reproduced  with  most  remarkable  exactness  in  the  "  corner- 
cell "  of  Cyclas.      But  here  the  organ  represents  an  individual 

^  This  seam  consists  of  a  series  of  microsomes,  as  Dr.  Watase  has  discovered. 


ii8 


BIOLOGICAL   LECTURES. 


cell,  while  in  Stentor  a  whole  crown  of  such  organs  is  formed 
without  any  division  into  cells.  Could  one  ask  for  a  clearer 
demonstration  ?  Are  we  not  forced  to  conclude  with  Gruber 
that  ^^  Jiowcver  great  tJic  diffcrciicc  bctivccii  an  infusoriiiDi  and  a 
highly  orga7iizcd  a7iimal,  it  cannot  be  a  qualitative  one.  We 
can  assume  that  the  same  vital  elements  serve  in  both  as  the 
foundation,  only  in  ever  nezu  combinations .  This  kinship 
declares  itself  very  clearly  in  the  correspondejice  of  many  organs 
of  the  infusoria  with  those  of  the  higher  organisms''  [I.e.  p.  i6). 


Fig.  3.  —  A,  '-Corner  cell"  of  Cyclas  cornea.     B,  Section  of  three  cells.     Other 

letters  as  in  Fig.  2. 


*'  So  finden  wir,"  says  Gruber,  "  in  einem  Thiere,  das 
schon  hoch  auf  der  Stufenleiter  der  vielzelligen  Organismen 
steht,  dieselben  Grundelemente  wieder  wie  in  dem  einzelligen 
Infusionsthierchen.   .   .   . 

''Wieder  und  wieder  der  Beweis  von  dem  gottlich  einfachen 
aber  auch  gottlich  gewaltigen  Gesetze  der  Einheit  der  Natur'' 

(p.  18). 

The  entoderm  of  Dicyema  illustrates  one  or  two  points  of  interest  in  this 
connection.  We  have  here  an  organ  in  which,  as  often  happens,  in  parasitic 
degradation,  cell-formation  has  been  dispensed  with.  The  entoderm  remains 
throughout  life  as  a  single  cell,  and  the  whole  process  of  reproduction,  for  ])oth 
kinds  of  embryos,  is  carried  on  /;/  the  body  of  this  cell  without  any  cellular  organs 
whatever. 

In  one  respect  this  unicellular  organ,  which  was  undoubtedly  once  multicellular. 


THE  IDADEQL/ACV  OF   THE   CELL-THEORY.       119 

What  is  the  difference  between  an  organization  embracing 
one  cell  and  one  embracing  two  or  many  cells  ?  Certainly  the 
essential  difference  cannot  lie  in  the  iiumber  of  cells.  We  must 
look  entirely  behind  the  cellular  structure  for  the  basis  of 
organization.  Even  a  highly  differentiated  organism  may 
reach  a  relatively  late  stage  of  development  just  as  well  without 
cell-boundaries  as  with  them,  as  we  see  so  well  illustrated  in 
the  insect  ^^^.  If  we  fall  back  on  the  number  of  nuclei  as  the 
essential  thing,  then  we  shall  have  to  reckon  with  multinucleate 
infusoria.  In  these  forms  do  we  not  see  that  it  is  always  the 
same  organism  before  us,  as  we  follow  its  history  through  the 
whole  cycle  of  nuclear  phases  ? 

The  essence  of  organization  can  no  more  lie  in  the  number 
of  nuclei  than  in  the  number  of  cells.  The  structure  which  we 
see  in  a  cell-mosaic  is  something  superadded  to  organization, 
not  itself  the  foundation  of  organization.  Comparative  embry- 
ology reminds  us  at  every  turn  that  the  organism  dominates 
cell-formation,  using  for  the  same  purpose  one,  several,  or  many 
cells,  massing  its  material  and  directing  its  mov^ements,  and 
shaping  its  organs,  as  if  cells  did  not  exist,  or  as  if  they  existed 
only  in  complete  subordination  to  its  will,  if  I   may  so  speak. 

In  the  phenomena  of  regeneration  and  embryogenesis  we 
find  abundant  evidence.  For  the  present  I  must  limit  myself 
to  a  few  features  of  development. 

Perhaps  the  peculiar  formation  of  the  embryo  Toad-fish 
(Batrachus)   is  as  instructive  a  case  as  I  am  acquainted  with. 

is  quite  unique,  for  it  may  become  the  receptacle  of  nuclei  Ijelonging  originally 
to  other  cells;  in  other  words,  it  becomes  multinucleate,  not  by  the  multiplication 
of  its  own  nucleus,  but  by  the  acquisition  of  exotic  nuclei. 

The  acquired  nuclei  are  what  I  have  called  elsewhere  the  "residual"  nuclei, 
which  are  left  over  when  the  formation  of  "  infusoriform  embryos  "  ceases.  Each 
of  these  nuclei  enters  into  vital  relations  with  the  cell,  and  each  undergoes  the 
differentiations  characteristic  of  the  true  entoderm  nucleus,  so  that  in  the  end  they 
can  only  be  distinguished  by  their  positions.  This  seems  to  show  that  the  differ- 
entiation of  nuclei  may  be  controlled  by  the  cell  to  which  they  are  transplanted. 

One  of  IJoveri's  observations*  shows  that  the  same  may  be  said  of  the  chromo- 
somes. One  or  more  of  the  chromosomes,  normally  eliminated  in  the  polar 
globules,  are  sometimes  carried  into  the  cleavage-nucleus..  The  supernumerary 
chromosomes  here  undergo  the  regular  transformations,  quite  unlike  those  which 
they  show  when  carried  out  in  the  polar  globule. 

*  Zellen-Studien.     Heft  2,  pp.  171  -  175. 


I20  BIOLOGICAL   LECTURES. 

If  one  will  take  the  trouble  to  compare  this  formation  with  the 
ordinary  type  of  teleostean  development,  he  will  not  fail  to  see 
that  the  organizing  forces,  whatever  they  may  be,  operate  to 
form  an  embryo  under  peculiar  difificulties.  It  will  be  seen 
towards  the  end  of  embryogenesis  that  the  material  of  the 
germ-ring,  owing  to  the  enormous  size  of  the  ^^g,  has  to  travel 
over  quite  a  long  distance,  in  order  to  reach  the  embryo.  A 
very  thin  bridge  of  cells  connects  the  hind  end  of  the  embryo 
with  the  closing  germ-ring,  and  this  bridge  is  formed  by  the 
migrating  cells  of  the  germ-ring.  What  determines  this 
wholly  exceptional  rnovement  of  the  cell-material  required  to 
form  the  embryo  1  Is  it  possible  that  the  cells  move  as  so 
many  independent  individualities }  But  they  do  move,  and 
no  doubt  in  obedience  to  directing  influences,  acting,  not  in 
the  cells  as  individuals,  but  in  and  through  the  entire  forma- 
tive material,  irrespective  of  cells. 

Whoever  doubts  this  would  do  well  to  study  more  faithfully 
the  living  embryo  during  its  formation.  If  the  cell-ghost 
should  still  haunt  his  vision,  I  would  suggest  still  another  field 
for  study.  I  would  suggest  first  of  all  that  he  try  to  get  as 
clear  a  notion  as  possible  of  the  formation  of  the  archenteron 
in  Amphioxus,  Petromzyon,  and  the  Frog.  The  case  of  the 
reptile  might  then  be  studied  with  profit.  Next  the  ''  chorda- 
canal  "  of  mammals,  and  finally  Kupffer's  vesicle  in  the 
teleost. 

There  is  no  longer  any  doubt  in  my  mind  —  and  here 
lam  in  accord  with  most  authorities  on  this  subject  —  that 
this  little  vesicle  is  a  reminiscence  of  the  archenteron.  The 
development  of  Gecco,  as  traced  by  Ludwig  Will,  removes,  as 
I  think,  the  last  doubt  on  this  point. 

If  the  development  of  Kupffer's  vesicle  be  studied  in  the 
light  of  its  phylogenetic  significance,  and  studied  in  the  living 
as  well  as  the  dead  ^gg,  I  cannot  help  thinking  that  candid 
reflection  on  the  facts  will  be  sufficient  to  force  conviction  to 
the  standpoint  here  taken. 

Having  learned  the  meaning  of  the  vesicle,  one  should  trace 
step  by  step  its  mode  of  origin  in  the  pelagic  fish-egg.  Here 
one  may  see  this  remnant  of  an  archenteric  cavity  arise,  not 


THE  INADEQUACY  OE  THE   CELL-THEORY.        121 

inside  the  embryonic  tissues  as  in  the  eggs  of  fresh-water 
fishes,  but  actually  outside  the  tissues  on  the  inner  face  of  the 
embryo,  near  its  posterior  end.  Its  whole  ventral  and  lateral 
boundary  is  formed,  not  by  archenteric  cells,  but  by  a  periblastic 
layer  often  as  thin  as  the  wall  of  a  soap-bubble,  and  completely 
free  from  all  nuclei.  It  does  not  even  arise  as  a  single  cavity, 
but  as  numerous  minute  cavities  that  look  like  a  cluster  of 
granules.  These  expand,  flow  together  gradually,  and  finally 
form  one  bubble-like  vesicle  projecting  almost  wholly  into  the 
transparent  yolk.  Having  attained  a  maximum  size,  its  slightly 
concave  roof  becomes  more  and  more  deeply  hollowed  out,  and 
thus  it  comes  to  inclose  more  and  more  the  cavity,  while  the 
latter  gradually  shrinks  in  size,  and  finally  vanishes  as  the  true 
cell-walls  close  up.  Such  is  briefly  the  history  of  this  floor-less 
form-reminiscence  of  what  is  a  more  substantial  rudiment  in 
many  other  embryos. 

This  remarkable  reproduction  of  a  form-phase  that  is  to  last 
only  for  a  few  hours  and  then  pass  away  without  leaving  a 
visible  trace  of  its  existence,  cannot  be  explained  as  due  to  cell- 
formation  nor  as  the  result  of  individual  action  or  interaction 
on  the  part  of  the  cells.  The  embryonic  mass  acts  rather  as  a 
//;///,  tending  always  to  assume  the  form  peculiar  to  the  state  of 
development  reached  by  its  "■  essential  architectonic  elements  " 
(Briicke)  —  elements  that  are  no  less  real  because,  like  the  atom 
and  molecule,  they  are  too  minute  to  be  seen  by  the  aid  of  our 
present  microscopes. 

That  cells  as  such  do  not  participate  in  this  fomiative  act,  is 
shown  by  the  mode  of  development  of  the  vesicle  and  by  the 
absence  of  cells  in  its  ventral  and  lateral  walls.  This  fact,  the 
absence  of  cells,  has  actually  been  urged  recently  against  the 
identity  of  the  structure  with  Kupffer's  vesicle,  —  an  error 
which  one  is  likely  to  fall  into  only  while  under  the  delusion 
that  acellular  walls  cannot  be  homologous  with   cellular  walls. 

The  evidence  furnished  by  Kupffer's  vesicle  will  doubtless 
lose  much  of  its  force  with  those  who  have  not  had  an  oppor- 
tunity to  study  the  subject  sufficiently  to  form  an  independent 
opinion  about  it.  To  some  who  are  better  acquainted  with  the 
structure,  its  meaning  may  still  appear  to  be  somewhat  prob- 


122  BIOLOGICAL   LECTURES. 

lematical,  and  the  evidence  drawn  from  it  as  therefore  unsatis- 
factory. It  would  be  useless  in  such  a  case  to  urge  the  point, 
and  also  wholly  needless,  as  examples  abound  that  are  not  open 
to  such  objections. 

The  form-changes  by  which  the  fish  blastodisc  passes  into 
the  germ-ring  stage  are  examples  of  this  kind.  It  is  well 
known  that  the  transformation  of  the  blastodisc  just  before 
the  appearance  of  the  germ-ring  is  quite  rapid,  at  least  in  the 
pelagic  fish-egg,  and  also  qjiitc  independent  of  cell-formation. 
The  discoidal  germ-rilass  suddenly  thins  out,  but  not  uniformly 
in  all  parts.  The  half  of  the  disc  in  which  the  embryo  is  to 
be  formed  remains  thick,  anticipating  as  it  were  the  axial  con- 
centration which  is  to  follow,  while  the  half  lying  in  front  of 
this  is  rapidly  reduced  to  a  thin  epithelial  membrane.  This 
r^'^/V?;/«/ differentiation  of  the  outer  layer  and  the  concomitant 
formation  of  the  germ-ring,  including  the  forward  movement 
of  the  embryonic  plate  (''head  process"),  which  advances  in 
an  axial  direction  to  the  very  centre  of  the  disc,  are  indubi- 
tably accomplished,  not  by  the  aid  of  cell-formation,  but  by 
formative  processes  of  an  unknown  nature,  but  nevertheless 
real  and  all-controlling.  Cell-formation,  to  be  sure,  goes  on, 
but  it  seems  to  me  certain  that  it  has  no  directive  influence 
on  the  formative  processes.  The  cleavage  runs  on  from  begin- 
ning to  end,  regularly  or  irregularly,  without  modifying  in 
any  essential  way  the  form  of  the  blastodisc.  All  at  once, 
when  this  segmentation  has  been  carried  to  a  certain  point, 
the  transformation  sets  in  and  goes  rapidly  on,  without  inter- 
rupting cell-formation,  but  to  all  appearance  quite  indepen- 
dently of  it. 

In  the  axial  concentration  of  the  very  broad  embryonic  plate 
we  see  a  formative  process  that  can  have  nothing  whatever  to 
do  with  cell-division.  Again,  in  the  establishment  of  the  caudal 
end  of  the  embryo,  long  before  that  part  of  the  germ-ring  which 
represents,  historically  at  least,  this  end  can  be  brought  into 
place,  we  have  another  decisive  test  of  formative  power  assert- 
ing itself,  not  only  independently  of  cell-division,  but  also 
against  all  the  obstructions  interposed  by  the  yolk.  This  pre- 
potency of   the  "plastic  power"   (Schwann)   is  seen  to  great 


THE  INADEQUACY  OF  THE   CELL-THEORY.       123 

advantage  in  the  pelagic  fish-egg,  but  still  better  in  the  Toad- 
fish-egg.  It  is  needless  to  cite  further  examples  of  this  sort, 
for  the  embryology  of  every  animal  is  full  of  them,  and  no  one 
can  fail  to  find  who  looks  for  them. 

If  the  formative  processes  cannot  be  referred  to  cell-division, 
to  what  can  they  be  referred  t  To  cellular  interaction }  That 
would  only  be  offering  a  misleading  name  for  what  we  cannot 
explain  ;  and  such  an  answer  is  not  simply  worthless,  but  posi- 
tively mischievous,  if  it  put  us  on  the  wrong  track.  Loeb's 
experiments  in  heterogenesis  furnish  a  refutation  of  the  inter- 
action theory.  The  answer  to  our  question  may  be  difficult  to 
find,  but  we  may  be  quite  certain  that  when  found  it  will  recog- 
nize the  regenerative  and  formative  power  as  one  and  the  same 
thing  throughout  the  organic  world.  It  will  find,  as  Wiesner 
has  so  well  insisted,  a  common  basis  for  every  grade  of  organi- 
zation, and  it  will  abolish  those  fictitious  distinctions  we  are 
accustomed  to  make  between  the  formative  processes  of  the 
unicellular  and  multicellular  organisms.  It  will  find  the  secret 
of  organization,  growth,  development,  not  in  cell-formation,  but 
in  those  ultimate  elements  of  living  matter,  for  which  idiosomes 
seems  to  me  an  appropriate  name. 

What  these  idiosomes  are,  and  how  they  determine  organi- 
zation, form,  and  differentiation,  is  the  problem  of  problems 
on  which  we  must  wait  for  more  light.  All  growth,  assimi- 
lation, reproduction,  and  regeneration  may  be  supposed  to  have 
their, seat  in  these  fundamental  elements.  They  make  up  all 
living  matter,  are  the  bearers  of  heredity,  and  the  real  builders 
of  the  organism.  Their  action  and  control  are  not  limited  by 
cell-boundaries.  As  Heitzmann  and  others  have  long  insisted, 
the  continuity  of  these  elements  is  not  broken  by  cell-walls. 
The  organization  of  the  ^g^^  is  carried  forward  to  the  adult  as 
an  unbroken  physiological  unity,  or  individuality,  through  all 
modifications  and  transformations.  The  remarkable  inversions 
of  embryonic  material  in  many  eggs,  all  of  which  are  ordci'ly 
arranged  in  advance  of  cleavage,^  and  the  interesting  pressure 
experiments  of  Driesch  by  which  a  new  distribution  of  nuclei 
is  forced  upon  the  ^t'g'g,  without  any  sensible  modification  of  the 

1  As  will  be  shown  later. 


124  BIOLOGICAL   LECTURES. 

embryo,  furnish,  as  I  believe,  decisive  proof  of  a  definite 
organization  in  the  ^%g,  prior  to  any  cell-formation.  The  opinion 
expressed  by  Huxley  in  his  review  of  "The  Cell-Theory,"  in 
1853,  forms  a  fitting  conclusion  to  this  introductory  sketch. 

"They  [the  cells]  are  no  more  the  producers  of  the  vital 
phenomena  than  the  shells  scattered  along  the  sea-beach  are 
the  instruments  by  which  the  gravitative  force  of  the  moon 
acts  upon  the  ocean.  Like  these,  the  cells  mark  only  where 
the  vital  tides  have  ^een,  and  how  they  have  acted. "^ 

1  British  and  Foreign  Medico-chirurgical  Review,  Vol.  XTI,  p.  314.     Oct.,  1853. 


SEVENTH     LECTURE. 

BDELLOSTOMA  DOMBEYI,    LAC. 

A   STUDY   FROM  THE   HOPKINS  MARINE   LABORATORY. 

Problems  in  Biology  are  inexhaustible,  they  renew  them- 
selves continually.  They  appear  with  kaleidoscopic  changes 
to  successive  generations  of  men,  who  receive  them  to  study 
in  new  light  and  from  new  standpoints.  The  results  of  these 
studies  are  not  all  as  stable  as  the  problems  themselves. 
These  results  present  themselves  to  us  as  facts,  and  as  theories 
based  on  facts.  Although  one  well-established  fact  is  worth 
much  speculation  about  its  significance,  yet,  without  the  aid 
of  well-considered  theories  concerning  the  causes  which  lie 
back  of  the  facts  and  the  meaning  of  the  facts  in  themselves, 
progress  were  well-nigh  impossible. 

These  are  trite  sayings,  but  they  have  very  appropriate 
applications  to  the  problems  of  the  nature  and  functions  of 
the  ear  at  the  present  time.  The  general  problems  of  the 
morphology  and  physiology  of  the  vertebrate  ear  are  much 
the  same  as  they  were  when  first  taken  up,  for  the  two  ques- 
tions, *'How  is  the  vertebrate  ear  constructed.^"  and  "How 
does  it  operate.-*"  still  express  the  aims  of  our  researches  in 
this  field  as  well  as  they  did  when  man  first  began  to  study 
into  his  auditory  anatomy.  But  our  conception  of  the  manner 
in  which  these  problems  are  to  be  solved  at  the  present  day  is 
no  longer  what  it  was  fifty  years  ago,  or,  indeed,  ten  years  ago. 
We  now  appreciate  the  full  force  of  the  requirements  which  the 
present  condition  of  morphological  and  physiological  science 
demands  in  the  investigation  of  these  problems.  To  know 
the  structure  and  function  of  our  own  ear,  we  find  it  not  only 
necessary  to  study  the  adult  anatomy  and  function  of  the  ear 
in  man,  but  also  in  cvcjy  otJier  vertebrate  form  as  far  as  pos- 


126  BIOLOGICAL  LECTURES. 

sible.  Nor  can  we  stop  here.  We  must  trace  out  the  ontogeny 
of  this  organ  in  all  those  forms  whose  adult  anatomy  we 
study,  and  in  so  doing  apply  the  known  laws  of  physics  and  of 
chemistry  to  the  development  of  their  forms  and  contents.  We 
must  trace  out  the  phylogenetic  development  of  the  ear  by  the 
comparative  study  of  what  we  have  gained  from  the  above  out- 
lined investigations,  combined  with  knowledge  from  two  sources 
yet  untouched,  viz.,  the  morphology  and  physiology  of  those 
sense-organs,  genetically  related  to  the  ear  sense-organs,  and 
the  scanty  store  of  facts  pertaining  to  our  problems  which 
palaeontology  can  give  us.  Investigations  undertaken  on  a 
basis  less  broad  than  this,  or  which  do  not  fall  within  some 
one  of  the  categories  above  mentioned,  are  sure  to  fall  far 
short  of  the  solution  in  the  first  case,  and,  in  the  second  case, 
to  be  of  little  or  no  service  in  the  general  progress  toward  the 
final  solution  of  these  problems. 

It  is  thus  made  apparent,  I  think,  that  although  the  physio- 
logical problem  is  not  as  extensive  as  the  morphological,  it  is 
not  for  that  reason  less  difficult  or  more  likely  of  an  early  solu- 
tion, for  its  final  solution  depends  quite  as  much  upon  our 
advances  in  a  knowledge  of  the  anatomy  and  physiology  of 
the  central  nervous  system  as  upon  experiments  upon  the  ear 
itself.  With  this  prospect  of  long-postponed  final  solution, 
facts  which  have  direct  bearing  upon  any  of  the  fundamental 
topics  of  ear  physiology,  are  all  the  more  valuable.  One  such 
fact  I  wish  to  announce,  viz.,  that  there  is  at  least  one  verte- 
brate which  does  not  depend  upon  its  internal  ears  for  the 
equilibration  of  its  body.  I  had  previously  concluded  that  the 
semi-circular  canals  were  not  organs  of  equilibration,  and  inci- 
dentally during  my  anatomical  work  I  was  able  to  determine 
that  the  ear  of  this  vertebrate  is  in  no  way  more  concerned  in 
maintaining  the  position  of  its  body  in  space  than  are  the  other 
sense  organs. 

In  the  lectures  for  1891,  I  brought  to  your  attention  certain 
facts  and  arguments  to  illustrate  the  gradations  of  structure 
of  the  ear  found  among  vertebrate  animals,  which  have  led  up 
to  the  production  of  the  human  ear.  And  I  showed  the  man- 
ner in  which  the  ear  of  Marsipobranch  fishes  presents  us  with 


BDELLOSTOMA    DOMBEYL    LAC. 


27 


the  simplest  form  of  this  organ  now  in  existence.  In  continu- 
ance of  my  investigations  of  this  important  organ,  it  became 
necessary  for  me  to  study  in  the  living  condition  some  repre- 
sentative of  this  group  of  fishes,  of  which  we  have  only  two 
species  in  American  waters,  viz.,  the  Myxine,  or  Hag-fish,  of 
our  Atlantic  coast,  which  is  found  from  Greenland  to  Cape 
Cod,  and  the  Bdellostoma  of  the  Pacific  coast,  which  has  been 
found  along  nearly  the  whole  Pacific  coast-line  of  both  North 
and  South  America.  In  reply  to  a  letter  of  inquiry  addressed 
to  President  Jordan,  of  Leland  Stanford  Jr.  University,  who  is, 
as  you  know,  preeminent  for  his  knowledge  of  American  Ich- 
thyology, I  learned  that  Bdellostoma  occurs  in  great  abundance 
in  the  Bay  of  Monterey  and  that  it  could  be  obtained  there  with 
comparative  ease.  These  two  factors  determined  the  direction 
of  my  journey,  and  I  accepted  the  kind  invitation  extended  me 
by  Profs.  C.  H.  Gilbert  and  O.  S.  Jenkins  of  Stanford  Univer- 
sity, placing  the  facilities  of  the  Hopkins  Seaside  Laboratory  at 
my  disposal.  This  marine  station  is  an  adjunct  of  Stanford 
University  and  has  just  passed  through  its  second  season. 

It  is  a  great  pleasure  for  me  to  be  able  to  tell  you  of  the 
true  scientific  spirit  in  which  the  affairs  of  this  rapidly  growing 
laboratory  are  conducted,  and  to  acknowledge  the  generous 
assistance  accorded  me  by  the  directors,  Drs.  Gilbert  and 
Jenkins.  In  the  interest  of  biology  in  America,  it  should  be 
made  widely  known  that  Mr.  Timothy  Hopkins  of  San  Fran- 
cisco, in  whose  honor  the  laboratory  has  been  named,  has  alone 
rendered  it  possible  to  found  the  institution,  and  he  has  pro- 
vided it  with  the  means  of  growth.  With  an  insight  into  both 
the  great  scientific  and  practical  importance  of  the  biological 
researches  rendered  possible  by  such  a  station,  an  insight  as 
rare  in  a  man  of  affairs  as  it  is  admirable,  Mr.  Hopkins  has 
supplied  the  indispensible  funds  for  the  undertaking,  and  has 
assured  the  directors  of  his  desire  to  have  the  station  grow, 
not  by  words  alone,  but  by  meeting  the  expenses  of  the 
additions  to  the  station  buildings  and  equipment.  In  doing 
this  Mr.  Hopkins  has  not  been  unmindful  of  the  library  which 
is  a  fundamental  need  of  all  research  work,  for  he  proposes  to 
make  and  keep  it  the  most  complete  collection  of  biological 


128  BIOLOGICAL   LECTURES. 

literature  in  connection  with  any  biological  laboratory  in  this 
country.  From  this  time  on  the  station  is  to  be  kept  in  readi- 
ness for  the  use  of  investigators  at  all  seasons  of  the  year. 

Thus  you  see  the  needs  of  biological  research  at  the  sea- 
shore are  appreciated  and  provided  for  on  the  Pacific  coast  in 
a  manner  worthy  of  emulation  by  men  of  means  on  this  side 
of  the  contii^nt.  How  long  must  we  wait  for  the  needed 
financial  support  of  our  permanent  station  here  }  Our  needs 
areurgent,  and  they  should  be  met  at  once.  Here  is  a  great 
opportunity  which  will  hardly  recur  in  this  generation. 

The  Hopkins  Seaside  Laboratory  stands  near  the  beach  on 
a  rocky  point  forming  part  of  the  peninsula  which  constitutes 
the  southern  boundary  of  the  granite  basin  known  as  the  Bay 
of  Monterey.  It  is  in  the  town  of  Pacific  Grove,  two  miles 
distant,  west  from  Monterey,  and  128  miles  south  of  San 
Francisco.  The  station  consists,  at  present,  of  a  plain  frame- 
building,  very  similar  to  the  original  building  of  the  Wood's 
HoU  Laboratory,  though  additions  to  it  are  to  be  made  this 
year.  A  pump  and  tank  house  is  added  to  the  east  end  of  the 
building  for  supplying  the  station  with  sea-water,  which  is 
pumped  up  more  than  twenty-five  feet  above  the  sea  level  to 
the  supply  tank,  from  which  it  flows  through  the  various 
aquaria  in  the  building,  and  thence  into  the  large,  out-of-door 
ground  aquarium,  in  which  large  animals  and  class  supplies  of 
the  hardier  small  animals  are  kept.  The  fauna  and  flora  of 
the  Bay  of  Monterey  are  very  rich  ;  but,  until  they  are  more 
thoroughly  studied,  we  cannot  accurately  estimate  the  cer- 
tainly very  large  number  of  forms,  both  rare  and  common,  or 
the  abundance  of  the  individuals  of  the  species  most  valuable 
for  the  work  of  the  station. 

In  general,  we  may  say  that  the  fauna  and  flora  is  sub- 
tropical, and  it  is  rendered  so  by  a  very  constant,  almost 
unvarying  temperature,  which  averages  65^0  the  year  through, 
and  also  by  its  nearness  to  the  northern  bounds  of  the  tropical 
seas  of  Central  and  South  America. 

One  of  the  features  of  the  station  is  its  nearness  to  a 
Chinese  fishing  village,  from  which  much  of  the  material  for 
work  is  obtained.      Fish  are  caught  almost   entirely  by  means 


BDELLOSTOMA    DOMBEVI,   LAC.  129 

of  trawl  lines  ;  and,  while  nets  of  several  kinds  are  used  from 
boats,  no  pound  nets,  such  as  we  find  in  the  shallow  waters 
about  here,  are  used,  because  of  the  depth  of  water  and  the 
rocky  character  of  the  coast. 

On  arriving  at  the  station,  it  became  at  once  apparent  that 
I  should  have  to  depend  upon  the  Chinese  fishermen  for  the 
collection  of  my  material,  Bdellostoma  is  so  abundant  as  to 
be  pestiferous  to  the  fishermen  by  clogging  the  lines  with 
their  peculiar  tenacious  slime. 

Bdellostoma,  as  you  know,  belongs  to  the  so-called  Myxinoid 
fishes,  this  name  having  been  applied  to  them  on  account  of 
their  unusually  slimy  bodies.  The  first  of  these  fishes  to  be 
discovered  was  the  European  Hagfish,  which  is  identical  with 
our  Atlantic  coast  species,  and  it  has  been  classed  with  the 
Worms,  Mollusks,  Amphibia,  and  finally  with  the  Fishes, 
where  it  properly  belongs.  The  great  Linnaeus  called  it  a 
worm,  even  though  his  attention  was  called  to  its  affinity  with 
the  fishes.  Bdellostoma  lives  on  the  bottom  of  the  ocean,  out 
to  the  depth  of  one  hundred  fathoms  and  more,  but  seems 
occasionally  to  ascend  fresh-water  streams  for  short  distances. 
It  is  supposed  to  be  in  its  habits  more  or  less  parasitic  on  the 
Halibut,  agreeing  in  this  respect  with  Myxine,  which  is  para- 
sitic on  the  Codfish.  I  have  seen  large  skins  of  the  Halibut 
beautifully  deprived  of  all  contents  save  the  skeleton,  and  with 
but  a  single  opening  in  the  region  of  the  gills  to  show  where 
the  devastator  had  entered  the  body.  Bdellostoma  is  about 
twenty  inches  in  length  (an  average  size),  but  varies  from 
about  fifteen  inches  to  twenty-five  inches  in  length.  The 
relative  proportions  of  the  body  in  the  two  sexes,  as  well  as 
in  youth  and  age,  are  much  the  same.  The  body  is  cylin- 
drical in  shape,  but  flattened  from  side  to  side  in  the  tail 
region.  In  color  it  varies  from  light  pink  to  a  dark-purple 
brown.  The  color  has  a  pinkish  tinge  during  life,  owing  to 
the  shining  through  of  the  red  blood  in  the  vessels  of  the 
white  skin  below  the  surface  coloration  spoken  of  above.  The 
median  ventral  line  remains  uncolored  from  the  region  of 
the  yolk  duct  or  umbilicus  to  the  cloaca,  and  in  old  individuals 
the  snout  and  a  broad  stripe  on  the  ventral  surface  of  the  body 


130  BIOLOGICAL   LECTURES. 

is  white.  In  other  words,  as  age  increases,  those  parts  of  the 
body  which  come  into  frequent  contact  with  objects  other 
than  water  lose  their  purple  color.  The  color  grows  gradually 
darker  from  the  ventral  surface  to  the  dorsum.  The  skin  is 
attached  to  the  surface  of  the  body  of  the  animal  by  a  thin 
median  dor^l  ligament  and  by  a  broad  median  ventral  area  of 
trabeculous  processes.  The  gill  holes  show  a  narrow,  whitish 
border,  which  is  especially  well  marked  about  the  ductus 
oesophago-cutaneus,  or  the  tube  which  permits  the  water  to 
escape  from  the  oesophagus  without  going  through  the  gills 
(Fig.  9,  D).  The  cloacal  opening  is  edged  with  white.  Over 
the  region  of  the  eyes  the  skin  is  pigmentless  and  transparent, 
so  that  light  penetrates  freely  to  the  eye  below ;  but  this 
corneal  membrane  is  not  in  any  way  invaginated  or  fixed  to 
the  surface  of  the  eye,  and,  since  the  skin  in  this  region  is 
very  movable,  the  transparent  area  is  very  much  enlarged 
when  compared  with  the  size  of  the  eyes  (Figs,  i  and  5).  The 
latter  are  small  and  devoid  of  pigment  in  the  retina,  as  far  as 
can  be  discerned  from  the  exterior,  and  the  whole  bulb  is 
imbedded  in  a  fat  pad  between  the  two  diverging  cutaneous 
branches  of  the  V  nerve  where  they  issue  from  the  sides  of  the 
head.  The  fish  are  very  sensitive  to  light,  and  seek  for  cov- 
ering until  the  head  is  shaded,  when  they  come  to  rest,  it  may 
be,  with  most  of  the  body  exposed. 

Bdellostoma  is  not  provided  with  appendages,  i.e.,  pectoral 
or  pelvic  fins,  and  depends  for  locomotion  upon  movements  of 
its  body,  eel-fashion.  It  is  a  graceful  and  rapid  swimmer.  In 
the  aquaria  it  remains  most  of  the  time  quiet  upon  the  bottom, 
resting  upon  its  ventral  edge  or  side.  In  order  to  maintain  an 
upright  position,  i.e.,  back  uppermost,  it  is  necessary  for  it  to 
curve  the  body  more  or  less,  in  order  to  provide  a  base  of 
support.  Oftentimes  the  curve  is  slight,  as  is  always  the  case 
when  the  animal  is  in  poor  health.  The  normal  position  is 
that  of  a  right  or  left-handed  coil  ;  and  they  coil  both  ways, 
apparently  to  rest  the  muscles  occasionally  (Fig.  3,  a  to  //). 
Sometimes  the  whole  body  is  taken  up  in  the  formation  of 
the  coil ;  again,  often  only  the  posterior  part  is  used,  thus  the 
head-end  being  reserved  free,  and  held  straight  or  bent  into  an 


BDELLOSTOMA    DOMBEYI,   LAC.  131 

S-shaped  figure.  A  slight  disturbance  or  an  internal  irritation 
will  cause  them  to  uncoil  slightly,  when,  like  a  delicate  watch- 
spring,  they  recoil  and  vibrate  for  an  instant  before  coming 
back  to  rest  (Fig.  3,  a  and  b).  This  motion  is  one  of  the  most 
beautiful  illustrations  of  muscular  elasticity  which  I  have  ever 
seen.  As  shown  in  the  Fig.  3,  Bdellostoma  can  curve  its  body 
into  very  complicated  figures,  the  most  complex  being  the 
double  and  triple  knots  into  which  the  fish  can  quickly  tie 
itself  for  the  purpose  of  removing  anything  attached  to  the 
surface  of  its  body.  This  it  accomplishes  by  keeping  its  body 
in  motion  through  the  knot,  and  tying  up  as  fast  as  it  comes 
untied.  When  in  a  position  of  complete  rest,  the  fish  rests 
equally  well  with  only  a  slight  bend  in  the  head  or  the  tail 
region,  though  it  is  the  tail  that  is  normally  used  as  a  support 
for  the  body  to  lean  upon.  When  irritated  the  fish  discharges 
from  a  series  of  minute  holes  in  the  skin,  running  along  either 


o.  o.  o.  0.0.0,0,0.0.0,0.0 


Tonque  muscles 


^  Taiichiol  l?e£)  t  on . 


Fig.  I. — The  Cephalo-Branchial  region  of  Bdellostoma  dombeyi  seen  from 
the  left  side  to  show  the  truncated  anterior  end  of  the  body  and  its  complement 
of  feelers.  The  position  of  the  eye-spot  and  the  mutual  relations  of  the  external 
branchial  pores  and  the  thread  gland  pores  is  also  given,  ^  natural  size. 

side  of  the  body,  which  project  like  minute  nipples  above  the 
surface  of  the  skin,  a  milky-white  fluid,  which  almost  instantly 
disappears  from  sight  when  the  fish  is  in  the  water.  These 
holes  are  the  openings  into  the  so-called  mucous  sacs  or,  as 
I  shall  designate  them  hereafter,  the  thread  cell  pockets  or 
nida7nental  organs.  These  sacs  are  imbedded  in  the  muscles 
of  the  body,  and  not  in  the  subcutaneous  tissue,  as  Jackson 
affirms  in  his  recent  edition  of  Rollcston.  The  discharge  is  in 
the  form  of  minute  jets,  and  is  caused  for  the  most  part  by 
the  muscular  contraction  of  the  skin  about  the  body.  The 
fluid  is  composed  of  minute  bodies  about  the  size  and  having 
something  of  the  appearance  of  starch  grains.  Each  grain  is 
a  thread  cell,  and  was  originally  a  columnar  cell,  derived  from 


132 


BIOLOGICAL   LECTURES. 


the  skin  lining  the  pocket,  and  which  has  been  transformed 
into  one  continuous  thread  in  such  a  manner  that  when 
brought  into  contact  with  water  it  unrolls  itself  in  layers, 
much  like  a  spool  of  knitting-silk,  when  it  comes  to  pieces  in 
layers,  and  straightens  out  in  the  water  in  an  incredibly  short 
space  of  time.  After  such  a  discharge,  if  one  attempt  to  take 
the  fish  out  of  the  water,  one  will  notice  that  the  fish  is 
pushed  away  from  before  the  hand,  and  that  it  is  impossible 
to  touch  it  ;  and,  further,  that  there  is  an  invisible  something 
between  one's  hand  and  the  fish.  By  pouring  off  the  water, 
or  raising  the  fish  above  the  surface,  you  find  the  creature 
inclosed  in  a  transparent,  gelatinous  mass  of  about  the  con- 
sistency of  thick  Qgg  albumen,  which  is  extremely  slippery, 
and  yet  adhesive  and,  at  the  same  time,  not  readily  broken 
into  pieces,   notwithstanding    its   apparent    gelatinous   nature. 

A   single   fish  will  quickly  fill    a 
bucket  with  this  so-called  slime  ; 
ikx.     i.e.,  convert  the  water  into  such 
fgjI.CJ    a  thick  jelly.      But  the  amount  of 
v";'     solid  substance,  i.e.,  the  mass  of 
the  exploded  thread  cells  required 
••.*v*^v;<.;..i,c-  ^^  \\o\(\  the  water  together  in  this 

Fig.  2.  — To  illustrate  the  way  in    vvay,  is  not  equal  to  a  piece  of  tis- 

which  Bdellostoma  surrounds  itself    ^^^^  ^^^    ^^^^    ^^   ^^^  ^^^^^^ 

with  a  mass  of  tangled  threads,  in 

the  meshes  of  which  a  great  quan-    ^^  ^'^^  DUCKet. 

tity  of  water  is  held.    The  consist-        You  see  from  this  short  account 

ency  of    the   mass   is    that  of   egg    ^^^^   Bdcllostoma  is  provided  with 

a  simple  but  effective  means  of 
protection  from  its  enemies,  and  at  the  same  time  with  a  good 
nest-building  apparatus,  for  it  can  at  a  moment's  notice  secrete 
a  dwelling-place  exactly  fitted  to  its  body  without  stirring  out  of 
its  place,  no  matter  what  position  it  may  be  in.  Oftentimes  these 
nest-shaped  masses  are  brought  up  with  the  fish  from  the  bottom. 
Bdellostoma  is  not  so  much  of  a  parasite  as  it  is  commonly 
reputed  to  be.  It  lives  on  or  close  to  the  bottom  of  the  sea 
and  like  its  relative,  Myxine,  it  seems  to  prefer  mud-covered 
surfaces  in  which  it  may  partly  conceal  itself.  It  feeds  upon 
fishes  of  the  Teleost  group.      It   is   not   known  that  they  ever 


BDELLOSTOMA    DOMBEYI,   LAC.  133 

disturb  Elasmobranchs,  They  devour  their  own  eggs,  and  I 
have  frequently  taken  the  remains  of  small  squids  from  the 
stomachs  of  these  animals.  It  is  certain  that  they  do  penetrate 
the  bodies  of  such  fish  as  the  Halibut,  the  Flounder,  the  Rock 
Cod  and  Codfish,  though  there  is  not  the  slightest  evidence 
that  they  do  so  while  the  fish  is  in  the  living  condition.  They 
might  readily  do  so,  however,  and  the  fishermen  all  believe  that 
they  do  attack  living  fishes  and  bore  their  way  into  them.  This 
much  is  certain  ;  very  frequently  fish  are  taken  in  the  trawl 
nets  from  which  one  may  see  the  Bdellostoma  issuing  in  haste 
to  get  into  the  water  again.  These  fish  hulks  are  found  to  be, 
usually,  thoroughly  despoiled  of  all  their  soft  parts.  They 
retain  the  fish  form  by  means  of  the  skeleton  within  an  intact 
skin  —  intact  with  the  exception  of  the  small  hole  in  the  region 
of  the  gills  through  which  the  squirming  fish  was  seen  to  come. 
Since  Bdellostoma  bites  the  sardine-baited,  trawl-line  hooks  of 
the  fishermen  with  extreme  avidity,^  and  is  able  to  swallow 
pieces  of  fish  or  other  food  nearly  as  large  as  its  own  ordinary 
diameter,  it  does  not  seem  to  be  entirely  correct  to  designate  it 
a  strictly  parasitic  animal.  And  if  it  is  not  parasitic,  its  sense 
organs  i:an  hardly  be  said  to  have  been  degraded  by  parasitism. 
If  they  are  not  degraded,  they  must  represent  primitive 
conditions,  and  so  far  as  the  structure  of  the  nose,  eye  and 
ear  are  known  to  us,  they  contain  absolutely  no  anatomical 
characters  which  would  justify  the  conclusion  that  they  are 
degraded  from  a  more  perfect  ancestral  condition.  The  eye 
lies  beneath  the  skin,  it  is  true,  but  this  is  doubtless  a  stage  in 
the  phylogenetic  development  of  the  eye,  just  as  the  existing 
and  very  primitive  condition  of  the  nose  is,  without  question, 
a  stage  in  the  genesis  of  the  nose  of  higher  forms. 

The  head  end  of  Bdellostoma  is  obliquely  cut  off  from  above, 
downwards  and  backwards,  in  such  a  fashion  as  to  bring  the 
anterior  end  of  the  long  tubular  nose  at  the  extreme  front 
end   of    the  body  ;    and  since  this  anterior  nasal   aperture   is 

1  The  trawl-lines  are  often  brought  up  with  as  many  Bdellostomas  as  other  fishes, 
and  my  Chinaman  assured  me  that  sometimes  nearly  all  of  the  Jiooks  were  taken 
by  this  Ilagfish;  or,  as  he  expressed  it,  "  Evely  ho6k  —  one  Sliklostome."  i.e. 
Cyclostome  —  he  having  learned  the  scientific  name  of  the  creature  from  the 
students  of  the  Hopkins  Laboratory. 


134 


BIOLOGICAL   LECTURES, 


surrounded  by  four  elongate  conical  feelers,  and  is  further  under 
the  control  of  a  set  of  muscles  which  effect  its  movements  in 
all  directions  about  the  long  axis  of  the  body,  we  see  that 
Bdellostoma  is  provided  with  a  very  sensitive  and  effective 
organ  of  touch,  and  as  such  it  makes  continual  use  of  it. 
Each  of  me  feelers  is  erectile  ;  that  is  to  say,  it  may  be  laid 
back  against  the  side  of  the  head  or  thrust  out  in  any  given 
direction  at  the  will  of  the  creature  (Fig.  4).  Each  feeler  is 
richly  supplied  with  nerves  and  blood  vessels,  and  has  a  slender 
and  flexible,  though  very  tough  filament  running  through  it 
to  give  it  strength  and  to  help  in  keeping  its  form.     These 


Fig.  3. —  Ten  representations  of  the  positions  taken  by  Bdellostoma  at  rest 
(a,  b,  c,  dy  e,  /,)  and  in  motion  {g,  h,  i,  J),  a  and  b,  right-  and  left-handed  coils. 
c,  with  bent  tail  to  act  as  support  for  body,  i  and  /,  single  and  double  bow-knots, 
into  which  Bdellostoma  ties  itself  in  order  to  draw  its  body  through  the  knot  for 
the  purpose  of  removing  the  thread  cells  or  other  foreign  substances  from  the 
surface  of  the  body. 

sensitive  feelers  about  the  nostril  give  warning  of  the  presence 
of  solid  particles  in  the  water  which  is  being  respired,  for  a 
constant  stream  of  water  is  drawn  into  the  nose  to  pass  into 
the  mouth  through  the  hole  in  the  roof  of  the  palate  and 
thence  onward  to  the  gills.  The  genuine  nasal  nerve  end-organ 
is  the  simplest  in  structure  of  any  presented  to  us  by  the 
vertebrate  series,  and  consist  (Fig,  7)  of  seven  semi-oval  plates 
of  mucous  membrane  which  hang  from  the  roof  of  the  nasal 
cavity  down  into  the  stream  of  water  as  it  turns  downward 
to  pass  into  the  mouth.  These  plates  are  bilaterally  disposed 
in  sets  of  three,  on  either  side  of  the  median  plate,  which  is 


BDELLOSTOMA    DOMBEYI,   LAC.  135 

the  largest  of  the  seven.  The  others  decrease  in  size  from 
within  outwards.  The  median  plate  is  characterized  by  its 
larger  size,  and  the  possession  of  a  terminal  knob  at  its 
anterior  end.  This  knob  is  continued  forward  for  some  distance 
along  the  roof  of  the  nasal  tube  as  a  continually  decreasing 
ridge.  So  far  as  my  investigations  have  gone,  the  olfactory 
nerves  end  in  Bdellostoma,  as  they  do  in  Petromyzon,  on 
either  side  of  this  median  raphe,  so  that  we  now  know  that  all 
Craniate  vertebrates  possess  bilaterally  symmetrical  special 
sense  organs  since  neither  group  of  the  Cyclostome  forms  an 
exception  to  the  rule. 

The  eyes  in  Bdellostoma  have  been  considered  greatly 
degenerated,  and  this  view  is  still  generally  accepted  on  the 
strength  of  Johannes  Miiller's  view  of  their  condition.  I  feel 
assured,  from  a  preliminary  examination  of  the  eyes, —  and 
my  examination  is  more  extended  than  the  one  upon  which 
Miiller  based  his  conclusion,^  —  that  the  Bdellostoma  eye  really 
represents  a  phylogenetic  stage  in  the  differentiation  of  the 
vertebrate  eye.  Two  striking  features  of  this  eye  are  the  lack 
of  visible  pigment  in  the  retina  when  viewed  from  the  outside, 
and  the  absence  of  a  genuine  cornea.  From  a  study  of  the 
adult  condition,  it  is  highly  probable  that  the  skin  of  the  body 
is  never  drawn  into  the  formation  of  the  eye  as  we  meet  with 
it  in  the  fishes  ;  consequently,  neither  crystalline  lens  nor 
cornea  are  present.  The  original  optic  cup  budded  out  from 
the  growing  brain  wall  forms  all  there  is  of  this  creature's 
eyeball,  and  hence  it  stands  as  an  important  and  extremely 
interesting  intermediate  stage  between  the  Branchiostoma 
condition  and  that  obtaining  among  the  rest  of  the  sub-kingdom. 
The  large  transparent  oval  spot  over  each  eye  serves  as  a" 
cornea,  permitting  the  light  to  enter  the  eye  no  matter  how 
much  the  skin  may  be  moved  out  of  its  ordinary  position. 
The  eyes,  along  with  the  rest  of  the  body  beneath  the  skin, 
are  constantly  bathed  in  the  lymph  which  occupies  the  space 
between  the  skin  and  the  muscles. 

1  Kohl  (Zoolog.  Beitrage)  has  given  us  an  account  of  the  histology  of  the  eye  in 
Myxine  glutinosa  and  he  adheres  still  to  the  old  view  of  the  degeneracy  of  this 
organ. 


136 


BIOLOGICAL   LECTURES. 


The  ear  of  Bdellostoma  lies  imbedded  in  the  cartilage  of  the 
base  of  the  skull  and  below  a  thick  layer  of  muscle.  The 
membranous  portion  is  essentially  like  the  ear  of  Myxine, 
and  the  reader  is  referred  to  the  previous  volume  of  lectures 
where  I  have  described  the  Hagfish's  ear  in  considerable  detail. 

Bdellostoma  lacks  all  traces  of  the 
system  of  lateral  line  organs  so  far 
as  is  yet  known,  and  it  has  no  rep- 
resentatives of  the  other  specialized 
sense  organs  of  the  skin,  common 
to  most  fishes. 

Isolated  sensory  cells  are  the  only 
special  sensory  structures  yet  found 
in  this  animal's  skin.  The  absence 
of  these  surface  sense  organs,  to- 
gether with  the  entire  lack  of 
appendages,  renders  Bdellostoma  an 
extremely  valuable  animal  with 
which  to  perform  ear-function  ex- 
periments ;  this  is  due  in  great  part, 
of  course,  to  the  very  simple  condi- 
tion of  the  ear  itself. 

Upon  cutting  through  the  scale- 
less  and  relatively  thin  skin  along 
the  ventral  line,  the  body  muscles 
come  to  view.  Of  these,  there  are 
two  principal  layers  covering  the 
whole  body.  When  they  are  cut  through  along  the  ventral 
line,  from  the  mouth  to  the  cloaca,  most  of  the  viscera  are 
exposed.  In  the  branchial  region,  as  shown  in  Fig.  9,  we  find 
the  heart  with  its  large  ventral  aorta  running  forwards,  giving 
off  gill-arteries  as  it  goes,  in  such  a  manner  that  either  side 
receives  as  many  branches  as  there  are  gills  on  that  side.  The 
gills  themselves  are  compressed  sacks,  circular  in  outline,  which 
assume  a  sub-globular  shape  when  they  fill  with  water.  The 
current  of  water  which  we  have  traced  from  the  nose  into  the 
mouth,  passes  back  through  the  oesophagus,  and  then  out  into 
the  gills  by  as  many  short  tubes  leading  from  the  oesophagus 


Fig.  4.  —  A  full  front  view  of 
the  face  of  Bdellostoma.  n,  nasal 
aperture,  i,  2,  3  and  4,  the  tenta- 
cles or  feelers.  /  and  o,  the  inside 
and  outside  rows  of  teeth,  m,  the 
mouth.  T,  the  tongue,  which  is 
here  thrust  forwards  out  of  the 
mouth  and  nearly  conceals  the 
opening.  The  tongue  stands  here 
at  right  angles,  in  two  directions, 
to  its  usual  position  inside  of  the 
head.     nat.  size. 


BDELLOSrOMA    DOMBEYI,   LAC.  1 37 

as  there  are  gills.  After  entering  these  sacks  the  water  is 
forced  out  through  the  sides  of  the  body  through  other  short 
tubes  which  connect  the  gill-sacks  with  the  surface  of  the  skin. 
Here  they  form  the  circular  gill-holes  to  be  seen  on  the  side  of 
the  head  region  of  the  animal.  Two  features  in  the  arrange- 
ment of  the  gills  deserve  attention.  First,  the  large  tongue- 
muscle  seen  in  Figs.  5,  9  extends  backwards  among  the  gills,  in 
this  individual  separating  the  anterior  five  pairs,  effectually  pre- 
venting any  contact  between  the  gill-sacks  of  the  opposite 
sides  and  also  bringing  about  a  compression  of  the  sacks  in  this 


Fig.  5.  —  A  side  view  of  the  cephalo-branchial  region  of  Bdellostoma.  Some 
of  the  internal  organs  are  drawn  into  the  figure,  the  body  walls  being  thought 
transparent.  The  arrow  shows  the  direction  of  the  respiratory  current  of  water 
toward  the  nose.  T  \,  2,  3,  and  4,  the  tentacles.  77/,  the  teeth,  which  here  are 
erected  and  thrown  outwards  by  the  unfolding  of  the  tongue.  y\',  olfactory  organ. 
E,  the  ear.  /,  the  eye.  M,  the  club-shaped  tongue-muscle.  E,  the  external 
branchial  pores.  Tr,  the  thread  gland  pores.  S.  C,  the  spinal  cord.  A',  the 
kidneys.  //,  the  intestine.  Z,  liver.  //,  heart.  Below  and  behind  each  gill 
opening  is  seen  the  opening  of  a  thread  gland,  a,  above  the  figure,  the  single, 
median,  pharyngeal  tooth. 

region  whenever  the  tongue-muscle  is  in  action  ;  second,  the 
apparent  relation  of  the  point  of  bifurcation  of  the  branchial 
aorta  to  the  posterior  end  of  this  tongue-muscle.  The  number 
of  gills  varies  to  an  astonishing  degree,  and  the  significance  of 
this  variation  has  not  heretofore  been  the  subject  of  any  serious 
inquiry  so  far  as  I  am  aware.  There  are  two  series  of  facts 
concerning  this  flexibility  of  the  branchial  .system  which 
deserve  separate  consideration.  First,  the  number  of  gills  of 
individuals  from  different  localities  varies  from  6  on  either 
side  to  14  on  either  side,  with  the  observed  intermediate 
stages  as  follows: 


138 


BIOLOGICAL   LECTURES. 


Six  gills  on  both  sides,  6  on  one,  7  on  the  other  side,  and 
7  gills  on  both  sides.  This  series  is  from  the  Cape  of  Good 
Hope,  i.  c,  practically  Indian  Ocean,  and  was  discovered  by 
Johannes  Miiller  in  1834.  Miiller  originally 
gave  a  separate  specific  n^me  to  each  of  these 
varieties  but  later  concluded  that  they  formed 
only  a  single  species.  No  representatives  of 
the  series  with  more  than  7  gills  on  both  sides 
and  less  than  10  on  both  sides,  have  as  yet 
been  recorded,  or  so  far  as  I  know,  observed. 
This  leaves  a  gap  of  2  gills.  But  from  10 
gills  on  both  sides,  up  to  14  gills  on  both 
sides  the  series  is  complete  and  is  as  follows: 

10  gills  on  both  sides,  1 1  gills  on  both  sides, 

1 1  gills  on  one  side,  12  on  the  other,  12  gills 
on  both  sides,  1 2  on  one  side,  1 3  on  the  other, 
13  gills  on  both  sides  and  14  gills  on  both 
sides.  It  is  interesting  to  note  the  fact 
as  first  made  out  by  Willey  that  during 
its  larval  development,  the  number  of 
primary  gills  laid  down  in  Branchiostoma  ^ 
varies  from  about  8  to  16,  with  an  average 
number  of  14.  This  may  be  a  mere  coin- 
cidence, but  I  am  disposed  to  look  upon 
this  as  a  fact  of  fundamental  importance. 
Kowalewsky  first  studied  the  growth  of 
the  gills  in  Branchiostoma,  and  Willey  has 
greatly  increased  our  knowledge  of  the 
processes   of    differentiation    met    with    in 

these  organs.  Unlike  other  members  of  the  vertebrate  stock 
this  animal  has  the  gills  on  one  side  laid  down  before  those  of 
the  opposite  side  make  their  appearance,  but  this  is  a  mere 
retardation  and  not  an  essential  difference.  The  second  gill- 
slit  is  the  first  to  appear  and  is  soon  followed  by  the  first,  after 
which  increase  in  number  takes  place,  only  from  before  back- 

1  It  is  advisable  on  account  of  priority  to  use  the  term  Branchiostoma  in  place 
of  the  more  familiar  term  Amphioxus,  as  Prof.  E.  A.  Andrews  has  recently  pointed 
out  in  his  paper  on  Aft  Undescribed  Acraniatc.  Studies  Biol.  Lab.  Johns  Hopkins 
Univ.,  V,  no.  4,  1893. 


Fig.  6. — Two  thread- 
cells.  I,  unexploded, 
showing  two  crossing 
layers  of  the  threads.  2, 
partly  exploded  and  un- 
ravelled thread-cell,  a, 
a  portion  of  a  coil  which 
has  slipped  off  the  cell. 
b,  the  unravelled  thread, 
much  magnified. 


BDELLOSTOMA    DOMBEYI,   LAC.  1 39 

wards.  These  simple  primitive  slits  increase  in  number  until 
about  14  of  them  are  laid  down,  when  a  stage  is  reached  during 
which  no  more  slits  are  formed  in  the  antero-posterior  series. 
This  stage  has  been  designated  the  critical  stage  by  Willey. 
When  the  activities  of  growth  again  rhanifest  themselves  in 
these  organs  it  is  an  entirely  new  fashion  and  results  in  the 
splitting  of  each  primitive  gill-slit  into  two  by  the  downward 
growth  of  a  median  gill-bar  which  thus  separates  an  anterior 
from  a  posterior  portion  of  the  original  aperture.  After  this 
process  has  begun,  increase  in  the  number  of  gills  from  before 
backwards  again  takes  place  ;  but  is  now  evidently  related  to 
the  acquired  habits  of  the  animal,  as  I  have  already  pointed 
out  in  another  place. ^  In  the  matter  of  gills,  we  see  that 
Bdellostoma  approaches  very  close  to  Branchiostoma,  and  in 
this  sense  the  Myxinoid  retains  very  primitive  relations  of  its 
gill-apparatus.  To  return  to  the  question  of  the  variability  of 
the  gills  in  Bdellostoma,  what  can  be  its  significance.-*  Have 
we  to  do  with  an  increase  or  decrease  in  the  number  of  gills  of 
this  animal,  seeing  that  by  far  the  largest  number  of  individuals 
now  existing  have  either  10  or  12  gills  on  both  sides  of  the 
body }  I  think  there  can  be  no  doubt  as  to  the  answer.  We 
are  here  dealing  with  a  reduction  in  the  number  of  gills  and  in 
no  case  with  an  increase.  This  conclusion  is  supported  by  the 
fact  that  the  more  highly  differentiated  Marsipobranchs  have  a 
smaller  number  of  gills,  and  this  is  true  not  only  of  Myxine, 
which  belongs  to  the  same  group  as  Bdellostoma,  but  in  a 
greater  degree  of  the  Petromyzonts.  In  view  of  these  facts  it 
is  extremely  probable  that  the  ancestors  of  Bdellostoma  were 
provided  with  about  13  to  14  gills,  and  this  number  maybe 
taken  as  representing  the  numerical  relations  of  the  branchial 
apparatus  of  the  primitive  forms  of  the  vertebrate  stock 
generally.  The  relation  of  the  base  of  the  tongue-muscle  to 
the  gills  is  of  interest,  and  here  again  we  find  great  variability. 
Miiller  found  it  to  lie  entirely  in  front  of  the  gills  in  the  6  and 
7-gilled  forms  from  the  Cape  of  Good  Hope,  and  this  condition 
obtains  in  Myxine  so  far  as  known.  In  Bdellostoma  with  10 
or  1 1  gills  the  base  of  this  muscle  may  lie  between  the  6th  and 

^  Concerning  Vertebrate  Cephalogenesis. — Journal  of  AForpholo}:^',  TV,  1890. 


140 


BIOLOGICAL   LECTURES. 


8th  pairs  of  gills,  according  to  Putnam.  In  the  12  and  13-gilled 
forms  I  have  found  it  between  the  5th,  or  at  most,  the  6th  pairs 
of  gill-sacks. 

In  the  material  which  I  was  able  to  collect  at  Monterey  the 
following  proportions  of  the  several  variations  prevailed  : 

loi    individuals    had    ir    gills    on    both    sides. 


26 

' 

"      1 1 
and    12 

«       « 

one    side 

the  other  side. 

208 

< 

had    12 

«       << 

both  sides. 

II 

"       12 

"      " 

one   side 

and    13 

«       « 

the  other  side 

8 

' 

had    13 

«       (( 

both    sides. 

354 

total 

number  of  individuals 

counted. 

Fig.  7.  —  The  olfactory  organ 
seen  from  its  ventral  surface.  A\ 
nasal  tube.  Z,  the  nasal  plates, 
of  which  there  are  three  on  either 
side  of  the  median  raphe.  K. 
X  2    diameters. 


Fig.  8.  —  A  transverse  section  of  the 
olfactory  organ  of  Bdellostoma,  showing 
the  nasal  plates  cut  across  C,  and  also 
partly  in  surface  view,  S.  R^  the  raphe, 
and  Z,  the  lateral  wall  of  the  nasal  cap- 
sule.     X  4  diameters. 


Of  the  eight  1 1-12  variation,  where  the  position  of  the  gills 
was  noted,  four  had  11  gills  on  the  right  side  and  12  on  the 
left,  while  the  other  four  were  just  the  reverse,  with  12  gills 
on  the  right  side  and  1 1  on  the  left.  The  same  alternate  vari- 
ation holds  true  of  the  12-13  variation.  This  fact  of  alternate 
variation  proves  conclusively  that  the  variability  in  number  of 
gills  between  the  two  sides  is  in  no  way  connected  with  the 
formation  of  the  ductus  oesophago-cutaneus,  which  is  always 
upon  the  left  side. 

The  vascular  system  of  Bdellostoma  is  being  studied  in 
Prof.  Gilbert's  laboratory  at  Stanford  University,  and  I  need 
not  enter  into  the  interesting  relations  which  this  system  of 
organs    sustains    to    the    general    variability    of    this    animal. 


BDELLOSTOMA    DOME E VI,    LAC. 


141 


especially  with  respect  to  the  branchial 
is  shown  in  the  cut.  It  is  through  the 
that  the  blood  is  carried  to  the  walls 
of  the  gill  sacks,  by  means  of  the 
individual  branches  a,  one  of  which 
leaves  the  main  trunk,  so  long  as  it 
remains  unpaired,  for  each  gill. 

Owing  to  the  possibility  of  its  play- 
ing an  important  part  in  the  develop- 
ment of  the  variability  of  the  gills,  it 
is  desirable  to  examine  the  nature  of 
the  so-called  tongue  and  its  muscles  a 
little  more  in  detail  than  we  have  yet 
done.  In  Figs.  9  and  5  these  structures 
are  shown  as  they  appear  upon  slitting 
open  the  body  muscles.  The  tongue 
forms  a  somewhat  heart-shaped  plate, 
when  spread  out  flat  as  in  Fig.  4,  and 
is  composed  of  two  symmetrical  lateral 
pieces.  These  halves  each  bear  two 
rows  of  teeth,  and  during  life,  while 
in  the  mouth,  they  are  inclined  at  an 
angle  to  each  other,  thus  forming  a 
trough,  whose  shape  is  maintained  by 
the  sides  of  the  mouth.  When,  during 
life,  the  tongue  is  thrust  out  of  the 
body,  it  is  flattened  out  upon  the 
anterior  edge  of  the  solid  floor  of  the 
mouth  cavity,  as  shown  in  Fig.  5, 
when  it  is  in  the  best  possible  position 
for  the  use  to  which  it  is  put,  viz.y  the 
rasping  away  of  the  flesh  of  the  fish  to 
which  Bdellostoma  has  fastened  itself; 
or,  if  it  is  a  small  bait,  the  rapid  and 
certain  forcing  of  the  bait  into  the 
mouth  cavity.  The  mechanism  which 
effects  this  end  is  quite  complicated, 
and  I  need  not  enter  into  a  complete 


arteries,  whose  position 
large  median  vessel  A, 


Fig.  9.  —  A  ventral  view 
of  a  dissection  of  the  gills 
of  a  Bdellostoma  dombeyi, 
with  12-13  gil^s,  to  show  their 
relations  to  each  other,  to 
their  blood  supply,  and  to 
the  surface  of  the  body.  M, 
the  club-shaped  tongue  mus- 
cle. Z,  its  tendon.  ^.  s., 
branchial  sack,  f-rj,  the  ex- 
ternal branchial  pores  or  gill 
holes.  Tr.,  the  pores  of  the 
thread  glands.  A,  the  ven- 
tral aorta,  a,  the  branchial 
arteries.  D,  the  ductus  oeso- 
phago-cutaneus.  br.  /.,  the 
internal  branchial  tube.  H^ 
the  heart. 


142  BIOLOGICAL   LECTURES. 

description  of  it  here.  It  will  suffice  if  I  confine  my  remarks 
to  the  large  club-shaped  muscle  which  lies  between  the 
anterior  pairs  of  gills.  In  cross  section  the  muscle  is  seen  to 
be  composed  of  an  outer  thin  ring  —  the  section  of  the  thin 
cylindrical  muscle,  and  an  inner  solid  muscular  disc  —  the  sec- 
tion of  the  solid,  club-shaped  muscle,  which  is  made  up  of  two 
equal  literal  halves.  Johannes  Miiller  has  called  the  outer  one 
of  these  the  hollow  tongue  muscle,  and  it  certainly  does  at 
first  sight  seem  to  deserve  the  name. 

The  long  tendon  into  which  the  tongue  muscles  taper,  runs 
forward  in  a  groove  in  the  top  of  the  cartilaginous  floor  of  the 
mouth  until  it  reaches  the  posterior  border  of  the  tongue,  when 
it  splits  up  into  two  unequal  bundles  of  tendinous  fibrillae, 
which  run  forward  and  insert  into  the  upper  surface  of  the 
tongue  body.  These  slender  tendinous  slips  are  so  arranged 
that,  when  the  tongue  is  drawn  out  of  the  mouth,  the  carti- 
laginous bars  carrying  the  teeth  are  turned,  so  as  to  throw 
the  teeth  outwards  and  forwards  in  such  a  manner  that  their 
points  are  erected,  and  catch  readily  the  instant  the  club- 
shaped  muscle  begins  to  draw  it  back  into  the  mouth.  The 
teeth  are  corneous  structures,^  borne  upon  the  soft  teeth 
papillae,  and  the  teeth  of  any  one  row  are  more  or  less  fused 
together  at  their  bases,  so  that  when  separated  from  their 
papillae,  they  hang  together  in  a  row  or  plate.  (Figs.  4  and  5.) 
Oftentimes,  the  inner  tooth,  which  is  also  the  larger,  separates 
from  the  others,  and  the  outermost  tooth  of  the  row  is  not 
always  united  with  its  fellow.  Each  tooth  is  an  exceedingly 
sharp-pointed,  conical  body,  flattened  from  abov£  downwards, 
and  curved  from  without  inwards. 

1  I  have  made  a  special  examination  of  the  teeth  of  Bdellostoma  dombeyi  and 
Myxine  glutinosa,  and  although  I  was  desirous  of  finding  the  enamel  cap  described 
by  Beard  I  was  unable  to  do  so.  There  is  not  the  slightest  trace  oibone  in  any  of 
the  teeth  of  these  two  forms,  and  what  Beard  has  taken  to  be  such  is  doubtless 
much  hardened  horn,  produced  by  the  methods  used  by  this  author  in  preparing 
sections  of  teeth  for  microscopic  examination.  I  have  cut  a  large  number  of  the 
teeth  of  Bdellostoma  and  of  Myxine  and  have  found  no  difficulty  in  sectioning 
them  in  situ  when  imbedded  in  celloidin.  The  Myxinoid  teeth  are  cornefied 
sheaths  of  the  epidermal  elevations  on  the  tongue  plate,  and  in  adult  life  show  no 
trace  of  dentine  or  enamel. 


BDELLOSTOMA    DOMBEYI,   LAC.  1 43 

The  number  of  teeth  in  Bdellostoma  varies  as  much,  if  not 
more,  than  the  number  of  gills,  so  that  the  only  two  ''constant'' 
characters  which  Muller  could  find  upon  which  to  base  a  classi- 
fication are  both  of  them  extremely  variable.  The  limits 
of  the  variability  of  the  teeth,  so  far  as  known,  are  as 
follows :  — 

Bdellostoma  from  the  Cape  of  Good  Hope,  6-j  gills,  |||, 
li 111     12  112 

11  I  1  1'     11  I  12- 

Bdellostoma  from  coast  of  Chili,  10  gills,  ^  |^y  (Lacepede), 

11112      13  113 
11  I  11'     12  1  12- 

Bdellostoma  from  coast  of  California,  1 1-13  gills,  -|||,  \\  |  W. 

The  California  series  which  I  have  counted  is  the  only  one 
extensive  enough  to  give  opportunity  for  the  observation  of 
the  variations,  although  Muller  evidently  had  nearly  extreme 
forms  in  the  three  individuals  whose  dental  formulae  he  re- 
corded. 

In  22  individuals  with  11  gills  I  found  the  dental  formulae  to 

Kf^  1Q  follows  •  110  19      110  19        4   IJ).  I  IJ).      1     1_0_  110      1    10  I  10 

DC  as  lOllOWS  . 1  -g-  I  9,     J-    10  I  To»    ^     9    I    9  '     ^     9    |  1  0'    ^    1  0  |  1  0» 

1  10111  1  10111  1  10  111  3  11110  1  11110  5  11  11 

-"-  TO]  9'   -■-  "9  r9'  ^     10  I  10'  ^10  I  10'  ^      11  I  10'  ^      10  I  10' 

1  11  I  11   1  L2  I  \\       9  12  112 
^    1  1  I  10'  -^  "9  I  "9  ■'  *"  11  I  11- 

In  61  individuals  with  12  gills  the  following  dental  formulae 

nrrnrred  • 1    8- 1  lil     1    ^l&     8-9-11-0.     1    -9_  I  IJ).     1    _9_  1 10     O  J-0- 1  ^ 

occurrea .       ±  9  |  j^,    l  9]  9,   o  9]  9,   x  ^q]   9,   x  io|iO'^    9  |9' 

1    10  19     1    10  19       1 0   1  0  |j_o_     4  1 0  jiJi     6  10  110     7  j_o.  1 1 0 

-*■    To|9'     -•-    TO  I  TO'       ^^      9    19  '     ^     10  19  '     "     ITTI  IT)'      '       9    I  10' 

1    Ul  I  i_l    1  10  1 11     1   JJ.  1 1-0.     1  11 1  1-0-     10  11 1 10     3111 11 

^       9    I    9  '     -^     10|l0'      ^       9    I    9  '      -*■     10|    9'      ^^     10|l0'      ^     iTFIlO' 

-^  ixrii'o'  -^  if  111-  These  counts  were  made  on  consecutive 
animals  as  they  came  from  the  trawl  line,  and  must  represent 
fairly  the  dental  conditions  of  Bdellostoma  in  the  Bay  of 
Monterey.  Two  things  are  apparent.  First,  there  is  not  the 
least  relation  between  the  number  of  gills  and  the  number  of 
teeth  ;  and,  second,  the  teeth  are  subject  to  much  greater 
variation  than  the  gills,  notwithstanding  they  belong  to  the 
so-called  hard  parts.  Size  and  age  do  not  affect  the  dental 
formula. 

On  combining  the  dental  formulae  of  the  ii-gilled  and  12- 
gilled  variations,  we  find  the  following  numbers  to  obtain  for 
the  '^6  individuals  whose  dental  formulae  I  have  carefully 
counted  on  both  sides  of  the  dentiferous  plate. 


144 


BIOLOGICAL  LECTURES. 


No.  of 
Indivi- 
duals. 


1 

8 
1 
1 
3 
1 
2 
14 


4 

7 
1 
2 

1 
2 
1 
1 
13 
1 
8 
1 
1 
1 
3 


Predomi-       FroiTi  this  table  we  learn  that  more  than 

Dental  nant  Num- 

Formuia.    ber  of     sevcn-tcnths  of  the  entire  number  of  indi- 

Teeth. 

I  viduals    belong   to   three    groups,  and    over 


i_o 


9 


^10 


half  of  these  belong  to  the  group  in  which 
lo  teeth  occur  in  both  rows  oftener  than 
any  other  number.  We  have  to  do  with  a 
reduction  in  the  primitive  number  of  teeth. 
So  much  for  the  California  specimens. 

The  Chilian  specimens  seem  to  average  a 
larger  number  of  teeth,  for  Girard  counted  in 
his  type  specimen  of  14  gills  y||yI,  while 
Putnam  found  i|  1 1|  or  \\  |  W  in  the  ma- 
terial he  studied  from  Talcahuano  Bay, 
brought  to  this  country  by  the  Hassler  expe- 
dition, which  is  reported  as  having  10  gills. 
Lockington  gives  the  formula  as  ^^  I  Lo.^ 
which  harmonizes  with  what  I  find  to  be  the 
most  abundant  formula.  Lacepede's  example 
from  Chili  had  a  dental  formula  of  \^-|V, 
which  is  quite  unusual,  and  indicates  what 
we  may  expect  from  a  careful  study  of  a 
large  series  from  the  South  American  coast. 
I  fear  that  the  dental  formulae  published  in 
the  systematic  accounts  of  Bdellostoma  are 
based  for  the  most  part  on  counts  of  the 
teeth  of  one  side  of  the  tongue  only,  and  in 
this  way  only  can  I  account  for  the  bilateral 
symmetry  which  characterizes  them. 
The  reproductive  organs  of  Bdellostoma  are  extremely  simple 
in  their  structure,  and  are  composed  in  both  male  and  female 
of  a  simple,  double-layered  plate  of  the  peritoneum  which 
hangs  down  as  a  fold  from  the  dorsal  wall  of  the  body  cavity 
on  the  right  side  of  the  median  line  (Fig.  12).  The  ovary 
occupies  nearly  the  whole  extent  of  the  body  cavity  in  the 
female.  The  testis  occupies  only  the  posterior  part  of  this 
long  fold,  and  in  the  female  no  eggs  are  developed  in  this 
region.     In  hermaphrodites  the  two  divisions  of  this  organ  are 


1  0 

TO 


10 
1  0 


10 

10 

"i_o 
'9' 

1  0 
TO 


1  1 


t  1 


ii 
10 

1  0. 


\  Q. 


10 
10 


10 


10^ 

10  I 

11  111 

10  r  -^^ 

^  1  i 

TO  J 


12 

TO 
1 1 


12 
11 


BDELLOSTOMA    DOMBEYI,   LAC. 


145 


separated  by  a  notch  in  the  lower  edge  of  the  fold.  The  left 
organ  seems  never  to  be  developed  in  any  of  the  Myxinoids. 
In  all  cases,  so  far  as  my  observation  goes,  each  individual  is 
potentially  bisexual,  but  Bdellostoma  is  not  much  like  the 
Myxine  in  changing  its  sex  with  increase  of  age  ;  certainly  this 
condition  does  not  seem  to  be  so  clearly  expressed  in  Bdellos- 
toma as  in  Myxine.  For  whereas  in  Mixine  only  the  young 
animals  seem  to  be  males,  in  Bdellostoma  large  and  presumably 
old  animals  are  found  to  be  males  as  well  as  females,  and  both 


Fig.  10.  —  A  view 
similar  to  that  shown 
in  Fig.  9,  but  drawn 
from  a  ']-']  gilled 
Bdellostoma.  Let- 
tering the  same. 


formed  by  th 
one  side. 


Fig.  II.  —  The  branchial 
apparatus  of  Myxine,  seen 
from  the  ventral  face,  to 
show  what  the  changes  are 
which  have  made  Myxine's 
respiratory  tract  so  differ- 
ent from  Kdellostoma's.  It 
is  at  once  apparent  that  the 
only  structures  in  any  way 
chaftged  are  the  external 
branchial  tubes,  which,  by 
all  uniting  together,  have 
only  to  pierce  the  skin  at 
one  place,  ce.,  oesophagus, 
1-6  and  g.  s.,  the  branchial 
sacks,  br.  t.,  the  external 
branchial  tubes  of  the  first 
gill.  Z>,  the  short  duct 
e  union  of    all  the   gill   tubes  of 


sexes  are  found  among  the  smallest  individuals  taken.  The 
large  anterior  region  of  the  peritoneal  fold  is  always  ovary,  while 
the  much  smaller  posterior  region  of  the  fold  is  the  testicular 
region.  The  ovary  is  readily  distinguished  by  the  numerous 
eggs  in  many  stages  of  development,  while  the  testicular  part, 
which  is  separated  from  the  ovarian  part  by  a  notch  or  deep 
scallop  cut  in  the  border  of  the  fold,  is  to  be  distinguished  by 
its  clear  vesicles,  grouped  together  like  a  bunch  of  grapes. 
Of  course  a  crucial  test  of  the  character  of  the  small  vesicles 
is  the  presence  of  spermatozoa  in  the  testicular  part.  Tested 
in  this  way  many  individuals  were  found  to  be  ripe,  while 
among  the  females  very  few  were  found  to  contain   eggs  in 


146 


BIOLOGICAL   LECTURES. 


the  last  stages  of  ripening.  The  explanation  for  this  scarcity 
of  ripe  females  which  has  been  applied  to  the  case  of  Myxine, 
viz.,  that  the  pregnant  females,  when  the  egg-laying  time 
comes  on,  cease  to  eat,  and  consequently  are  not  to  be 
taken  either  in  baited  pots  or  on  trawl  lines,  must  suffice 
for  Bdellostoma  until  we  have  a  better  one.  Other  causes 
may  be  operative  here,  but  nothing  is  known  with  certainty 
of  the  ^nditions  of  life  which  surround  the  ^^'g  laying  and 
embryology  of  Bdellostoma. 


Fig.  12. —  A  side  view  of  the  sexual  gland  of  an  hermaphroditic  Bdellostoma 
dombeyi.  a  and  b,  cross-sections  of  the  gland  at  the  points  indicated  by  the 
arrows,  v,  the  dorsal  blood  vessel,  below  which  the  gland  is  suspended  as  a 
double  fold  of  the  peritoneum.  /.  ov,  ovary,  te^  testis.  E,  nearly  ripe  eggs. 
e,  very  young  ova.    /,  testicular  follicles. 

Some  individuals  of  Bdellostoma  are  truly  hermaphroditic, 
having  at  the  same  time  a  genuine  testis  with  ripe  sperm  and 
an  ovary  with  eggs  nearly  or  quite  ripe.  These  individuals  are 
rare,  so  far  as  my  experience  goes,  but  others  with  the  two 
organs  in  a  more  unequal  state  of  development  are  more 
numerous.  However,  by  far,  the  largest  number  of  individuals 
are  genuinely  male  or  female.  Males  are  much  more  numerous 
than  the  females,  but  this  statement  applies  only  to  the  catches 
which  I  had  the  opportunity  of  examining.  It  may  be  merely 
a  coincidence,  or  on  the  other  hand  it  may  faithfully  represent 
the  true  conditions  of  things  in  the  Bay  of  Monterey.  All 
things  considered,  I  believe  a  preponderance  of  males  represents 
the  ordinary  condition. 

The  sex  of  209  out  of  354  individuals  was  noted,  and  they 


BDELLOSTOMA    DOMBEYI,   LAC.  147 

are  distributed  between  the  males,  females  and  hermaphrodites 
in  the  manner  indicated  by  the  following  table  : 

Of  loi  individuals  having  1 1 

gills  on  both  sides,         .  61  were  males,  y]  were  females,  and  3  hermaphrodites. 
Of  26  individuals  having  1 1 

gills  on  one,  12  on  the 

other  side,     .         .         .    14     "         "       12    '.^*  "  '*    O  " 

Of  163  individuals  having  12 

gills  on  both  sides,        .  94     "         "      66     "  "  "    3  " 

Of  II  individuals  having  12 

gills  on  one  side  and  13 

on  the  other,         .         .     8     "         "        3     "  "  "    o  " 

Of  8  individuals  having  13 

gills  on  both  sides,        •     5     "         "'        3     "  "  "    o  " 

Totals,  182  121  6 

The  sexuality  of  the  Bdellostoma  does  not  appear  to  depend 
upon  size  or  age,  for  of  10  small  individuals  (under  15  inches) 
there  were  7  males  with  gills,  \\,  2  females  with  gills,  i|,  and 
I  female  with  gills,  yy- 

Of  1 5  large  individuals  (over  20  inches)  there  were  8  males 
with  gills,  i|,  I  female  with  gills,  l|,  5  males  with  gills,  l-i, 
and  I  male  with  gills,  l|. 

In  1875,  Anton  Dohrn,  the  founder  and  talented  director 
of  the  Zoological  Station  of  Naples,  first  clearly  defined  the 
hypothesis  of  degeneration,  and  fully  illustrated  its  application 
to  the  vertebrata  in  his  famous  paper,  ''Origin  of  Vertebrates." 
Dohrn  corrected  the  then  prevalent  ideas,  according  to  which 
all  the  simpler  forms  of  animals,  anatomically  considered,  were 
to  be  looked  upon  as  more  primitive  and  as  representing 
ancestral  stages  in  the  development  of  the  groups  to  which 
they  belonged.  He  was  not  fortunate  in  his  selections  of 
cases  of  degeneracy  among  vertebrates,  as  I  hope  to  make 
clear  to  you.  As  a  typical  case  of  true  degeneracy  we  have 
the  well-known  case  of  the  Tunicate,  which  during  its  devel- 
opment passes  through  a  stage  which,  according  to  the 
'' biogenetisches  Griindgesetz''  must  be  considered  to  be  strictly 
vertebrate  in  its  morphological  characters.  These  vertebrate 
characters  are  not  retained  by  the  Tunicate,  however,  but  are 
absolutely  destroyed  during  the  growth  of  the  larval  body,  so 
that  in  the  adult  condition  there  is  nothing  left  to  ever  remind 


148 


BIOLOGICAL   LECTURES. 


one  of  the  vertebrate  type  of  organization,  and  the  body  ever 
after  remains  in  this  inferior  condition  of  structure,  though  it 
produces  germs  which  in  their  development  attain  the  higher 
level  of  vertebrate  organization,  only  to  sink  back  to  the  lower 
level  of  Tunicate  structure. 


Fig.  13. —  A  view  of  three  ripe  eggs  of  Bdellostoma  dombeyi,  showing  their 
natural  size,  the  variations  in  shape,  the  manner  in  which  they  hold  together  by 
means  of  their  anchor  hooks,  and  the  position  of  the  suture  which  allows  of  the 
ready  separation  of  the  cap  from  the  body  of  the  egg  membrane,  a,  an  end  view 
of  an  egg  cap.  The  anchor  filaments  have  all  been  radially  spread  to  show  the 
spiral  arrangement  of  the  filaments  upon  the  cap  surface,  x,  the  anchor  head, 
y",  the  filament,  b,  a  side  view  of  another  cap.  st,  the  cap  membrane,  b,  the 
row  of  enlargements  forming  the  bases  of  the  filaments,  /  x,  the  anchor  heads. 
The  central  dot  in  a  shows  the  position  of  the  micropylar  funnel  which  leads  into 
the  micropylar  canal.  The  egg  membrane  is  composed  of  a  thin  genuine  vitelline 
membrane  and  a  thick  corneous  follicular  (granulosa)  membrane,  and  the  anchor 
threads  are  hollow  evaginations  from  the  end  parts  of  the  latter.  Natural  size, 
a  and  b  Y.  2  diameters.^ 


1  After  a  study  of  the  development  and  the  adult  condition  of  the  egg  mem- 
branes in  Bdellostoma  dombeyi  I  am  certain  that  Cunningham  is  in  error  in  calling 
the  egg  membrane  of  the  Myxinoids  a  vitelline  membrane.  The  corneous  part  of 
the  egg  shell  is  cellular  in  nature  and  the  cell  remnants  are  to  be  seen  in  the  ripe 
egg  shell.  The  anchor  hooks  are  formed  by  the  evaginations  of  this  granulosa 
layer  in  late  stages  of  egg  life,  due  to  the  outgrowth  of  solid  rods  of  the  vitelline 
membrane.  These  rods  appear  to  be  resorbed  before  the  ripening  of  the  egg  and 
thus  the  anchor  filaments  are  left  hollow.  The  Myxinoid  egg  is  thus  very  much 
like  other  fish  eggs  as  regards  its  envelopes.  An  illustrated  account  of  these 
facts,  among  others  is  ready  for  the  press. 


BDELLOSTOMA    DOMBEYI,   LAC.  149 

Thus  it  is  that  the  evidence  in  favor  of  progressive  simplifi- 
cation of  structure  (which  is  all  that  is  meant  by  the  term 
degeneracy)  depend  upon  two  factors : 

{a)  The  comparison  of  the  anatomy  of  the  fully  developed 
degenerate  animal  with  that  of  its  supposed  congeners.  In 
this  way  we  can  often  be  sure  that  the  less  complex  animal 
does  not  represent  any  of  the  ancestral  stages  common  to  its 
nearest  relatives.  This  is  the  anatomical  method,  and  {b)  by 
the  study  of  the  embryological  development  of  the  forms  under 
consideration.  This  is  the  embryological  method,  and  it  is  very 
generally  admitted  to  be  conclusive  whenever  it  can  be  shown 
that  either  the  embryonic  or  larval  stages  of  the  animal 
under  consideration  possess  a  higher  degree  of  morphological 
differentiation  than  is  possessed  by  the  adult  form.  e.  g. 
barnacles  (Cirrhipedes),  Tunicates.  In  many  instances  the 
embryological  history  may  be,  and  is,  so  shortened  as  to  give  no 
trace  of  a  higher  stage  of  existence  having  ever  been  enjoyed. 
e.g.  many  Tunicates.  Even  from  this  very  short  review  of 
the  degeneration  hypothesis,  it  is  evident  that  we  must 
conclude  that  a  pidori  there  is  much  reason  to  suppose  that 
any  given  animal  form  may  have  developed  from  a  more  highly 
organized  ancestor  by  a  process  of  simplification  as  to  assume 
that  it  has  developed  from  a  relatively  simpler  form  by  an 
unbroken  process  of  complication,  and  that  our  only  means 
outside  of  morphological  research  is  to  be  derived  solely  from 
the  life  habits  of  the  animal,  i.e.  whether  they  are  such  as  to 
favor  degeneracy  or  not.  In  saying  that  there  is  much  reason, 
on  a  priori  grounds,  to  assume  that  an  animal  has  degenerated 
or  developed  downward  to  its  present  condition  as  that  it  has 
developed  upward,  I  certainly  cannot  acquiese  in  the  view 
expressed  by  Dohrn  and  adopted  by  Lankester  that  there  is  as 
much  probability  in  favor  of  the  one  process  as  of  the  other, 
for  it  is  evident  that  cases  of  degeneracy  must  be  much  less 
common  than  cases  of  progression,  otherwise  the  Law  of 
Agassiz,  fully  established  by  Darwin,  would  not  be  so  easy 
of  observation  in  embryology  and  palaeontology.  The  law  of 
progressive  differentiation  is  so  universal  in  its  application  that 
we  are  on  safe  ground  in  always  considering  any  existing  form 


ISO 


BIOLOGICAL   LECTURES: 


as  the  result  of  a  series  of  progressive  changes,  or  viewing 
any  fossil  form  as  the  highest  of  its  kind  up  to  the  time  of  its 
existence,  unless  in  either  case  there  is  positive  proof  to  the 
contrary  ;  for  the  biogenetic  law  lays'  the  burden  of  proof 
upon  the  degenerationist.  Life  habits,  favoring  simplification 
or  obliteration  of  structure,  are  parasitism,  sessile  or  fixed 
life,  burrowing  and  hiding  in  crevices  and  holes,  and  indiscrim- 
inate and#:liffuse  food  habits,  while  free  and  unrestricted  motion 
within  the  aqueous  and  aerial  oceans  upon  and  over  their 
bottoms,  involving  the  pursuit  of  fleeing  prey  and  the  struggle 
with  other  forms  for  its  possession  and  for  life  itself,  are  highly 
favorable  to  increasing  complication  of  structure.  It  is  at 
once  evident  that  we  cannot  take  existing  vertebrates  and 
group  them  either  in  an  arbor-like  or  ladder-like  geneological 
arrangement,  and  at  the  same  time  express  the  true  relation- 
ships of  the  many  modifications  of  structure  which  have  been 
produced.  This  brings  us  to  the  consideration  of  the  question 
of  the  classification  of  Bdellostoma,  and  to  this  I  shall  return 
after  throwing  what  light  I  can  upon  the  conditions  under 
which  Bdellostoma  exists  and  the  probable  relations  which  this 
fish  bears  to  these  conditions  of  its  environments. 

What  evidence  can  we  bring  forward  to  show  that  ''  the  small 
and  degenerate  group  Cyclostomata''  as  Lankester  ^-  calls  them, 
are  not  degcficrate  Vcrtcbi'atcs  ?  In  previous  publications  I  have 
pointed  out  some  of  the  facts,  and  I  am  sorry  to  say  they  have 
not  been  accorded  that  consideration  which  they  merit  as 
anatomical  facts.  In  1889^  I  showed  that  ''the  higher  sense 
organs  of  the  Cyclostomata  are  all  paired^  since  the  nose  [i.e.,  the 
nasal  or  olf active  epithelinni)  exists  in  the  efjtbryo  as  zvell  as  the 
adult  in  tJic  form  of  two  circumscribed  areas  lying  07i  either  side 
of  the  media7i  line,  each  of  zvhich  receives  the  entire  iierve  supply 
ajforded  by  the  olfactoiy  nei^^e  of  its  side.  I  then  ventured  to 
predict  that  the  Myxinoids  would  show  the  bilaterally  sym- 
metrical or  paired  nasal  areas  as  distinctly  as  Petromyzon  does. 
I  can  now  state  that  my  conclusion  was  well  founded,  for  in 
Bdellostoma  we  have  the  nose  divided  into  right  and  left  halves 

1  Reprint  Article,  Vertebrates,  Eitcy.  Brit.  ed.  1887.     London,  1890. 

2  Concerning  Vertebrate  Cephalogenesis,  Journal  Morphology,  l'V,\'&go. 


BDELLOSTOMA    DOMBEYI,   LAC.  151 

by  a  median  plate  which  is  the  homologue  of  the  median  raphe 
of  Petromyzon.  In  Figs.  7,  8  is  shown  this  important  feature 
as  seen  from  the  ventral  surface  (inner  face)  of  the  nasal  organ. 
As  concerns  Bdellostoma's  eye,  we  know  very  little  of  its  adult 
structure  and  nothing  of  its  development,  and  the  conclusion 
that  it  is  a  degenerate  organ  in  lacking  a  lens,  choroid,  etc., 
and  being  entirely  below  the  surface  of  the  body  and  under  the 
skin,  is  purely  hypothetical,  for  it  can  just  as  well  represent 
a  stage  in  the  phylogenetic  development  of  vertebrates.  I 
believe  such  to  be  the  truth.  The  undegenerate  nature  of 
the  ear  I  have  already  established  in  another  publication. ^  On 
the  basis  of  our  knowledge  of  the  higher  sense  organs  we  may 
well  ask:  Why  are  the  Myxinoids  primitive  fishes  ?  instead  of 
''  Why  are  they  degenerate  vertebrates  }  "  The  following  con- 
siderations enable  us  to  understand  why  they  are  primitive  and 
not  degenerate: 

1 .  Their  unusually  great  geographical  distribution  indicates 
that  they  are  descendants  of  a  very  ancient  stock. 

2.  They  are  in  a  morphologically  undifferentiated  condition, 
as  compared  with  all  other  groups  of  craniate  vertebrates  and 
their  several  organs  show  no  certain  traces  of  degradation 
of  structure.  In  this  regard  I  have  examined  the  following 
organs:  skin  (here  the  absence  of  surface  sense  organs,  scales, 
except  the  teeth,  and  a  lateral  line  is  noteworthy  and  entirely 
unexplained;  they  are  not  degraded  but  Jiave  entirely  vanished 
from  adnlt  life),  muscular  system,  skeleton,  vascular  system, 
alimentary  system,  urino-genital  system  and  the  higher  sense 
organs,  eye,  ear  and  nose.  Of  these  latter  the  two  last  are 
normal  stages  in  the  development  of  the  vertebrate  stock, 
and  so  far  as  I  have  examined  the  structure  of  the  eyeball, 
its  lack  of  lens  and  eye  muscles  and  its  small  optic  nerve, 
I  have  found  no  conditions  which  are  not  harmonious  with  the 
view  that  this  eye  has  simply  never  been  highly  developed. 

The  degeneration  hypothesis  fails  completely  to  account  for 
Myxinoid  anatomy,  and  the  habits  of  the  animal  give  no 
grounds  for  this  assumption.  Certainly  the  natural  conditions 
surrounding  the  life  of  the  animal  as  far  as  we  know  them,  are 

1  Contributions  to  the  Morphology  of  the  Y.zx,  Journ.  Morphol.  VII,  1892. 


152  BIOLOGICAL   LECTURES. 

not  such  as  to  cause  the  extensive  retrogressive  development 
which  they  are  supposed  to  have  undergone  and  which  it  is 
assumed  has  affected  nearly  all  of  the  organs  of  the  body. 

It  seems  to  have  become  a  settled  belief  among  the  large 
majority  of  zoologists  of  both  morphological  and  systematic 
proclivities  that  the  number  of  gills  found  among  vertebrates 
never  rises  above  eight  pairs  in  existing  forms.  The  few  who 
have  recognized  the  true  state  of  the  case  have  had  little  to  do 
with  the  education  of  the  younger  men,  and  so  the  error  has 
continued  to  be  taught.  Lankester  ^  wrote  in  1 890  —  regarding 
the  gills  of  vertebrates,  ''The  pharyngeal  slits  follow  closely 
upon  the  mouth,  and  in  existing  Craniata  never  number  more 
than  eight  pairs."  Wiedersheim  ^  gives  seven  pairs  of  gills  as 
the  largest  number  occurring  among  craniate  vertebrates,  while 
Claus,  Huxley,  Jackson-Rolleston,  Hertwig  and  others  give  the 
number  varying  from  5  to  8,  but  never  greater  than  8.  They 
evidently  confine  themselves  to  Miiller's  statement  concerning 
the  number  of  gills  (6-7)  in  Myxinoids  and  to  the  known  facts 
concerning  Petromyzoa  (7)  and  the  Notidanidae  (^-y).  In 
1854  Charles  Girard  described  a  fish  from  the  coast  of  Chili 
which  he  called  Bdellostoma  polytrema,  and  which  he  found  to 
have  14  pairs  of  gills.  In  1873  Putnam  found  that  the 
Bdellostomas  of  the  Hassler  expedition,  collected  off  the  coast 
of  Chili,  had  10  pairs  of  gills.  Later  on  Lockington  (1878) 
described  a  similar  fish  from  San  Francisco  which  had  1 1  pairs 
of  gills.  These  are  the  only  original  observations,  with  which  I 
am  acquainted,  which  give  the  number  of  Myxinoid  gills  greater 
than  the  accepted  numbers  (6-1).  Yet  these  facts  have  been 
many  times  confirmed  by  such  men  as  Gunther,  1873,  Gill, 
1880,  and  Jordan  and  Gilbert,  1882,  who  gave  the  number  of 
gills  of  the  Pacific  Bdellostomid  as  1 1-14.  Notwithstanding  all 
these  published  accounts,  morphologists  have  completely  over- 
looked these  facts,  and  while  speculating  on  the  ancestral 
number  of  gills  of  vertebrates,  have  depended  for  the  most  pari 
upon  the  embryological  stages  of  Elasmobranch  and  Teleost 
fishes. 

1  Ency.  Brit.    Article  on  vertebrates. 
^  Grundriss  d.  vergl.  Anat.    Jena,  1893. 


BDELLOSTOMA    DOMBEYI,   LAC.  153 

I  have  already  referred  to  this  matter  in  connection  with  the 
brief  description  of  Bdellostoma's  gills,  but  it  is  sufficiently 
important  to  call  for  a  more  detailed  account,  in  which  I  shall 
try  to  bring  the  branchial  arpparatus  of  Bdellostoma  into 
harmony  with  the  primitive  condition  of  the  same  organs  in 
Branschiostoma. 

Having  shown  that  there  is  a  great  degree  of  variability  in 
some  of  the  organs  of  Bdellostoma,  it  will  be  in  place  to  seek 
for  the  conditions  which  keep  up  this  variability,  —  for  the 
conditions  must  be  present  conditions  and  in  no  sense  past 
ones.  Three  conditions  suggest  themselves  as  probably  con- 
cerned in  keeping  up  this  variability  among  the  Bdellostomas 
as  a  group  of  animals  of  common  descent  and  as  families  of 
individuals  living  under  common  conditions  in  circumscribed 
areas.  These  are  Geographical  Distribution,  Panmixia  and 
Hermaproditism. 

The  geographical  distribution  of  Bdellostoma  cannot  be 
satisfactorily  accounted  for  by  assuming  several  separate  crea- 
tions of  these  animals,  for  though  so  widely  distributed  on  the 
floor  of  the  Indo-Pacific  oceanic  depression,  all  its  morphologi- 
cal characters  and  its  life  habits  point  to  its  origin  from  a  single 
ancestor  at  some  place  in  the  South  Pacific  ocean.  Admitting 
the  common  descent  of  the  varieties  of  Bdellostoma,  the 
phenomena  connected  with  the  geographical  distribution  of 
animals  in  general  lead  us  to  conclude  that  Bdellostoma  has 
existed  for  a  very  long  period  of  time  and  that  it  has  been  but 
little  modified  during  this  long  period.  We  do  not  know  that 
it  has  always  been  as  variable  as  it  is  at  present ;  but  if  it  has 
been,  it  is  a  most  remarkable  case,  since  ordinary  ajiimals 
would  have  become  well  differentiated  into  distinct  species  during 
the  process  of  dispei'sion  over  such  a  great  territory  and  the 
consequent  operating  of  more  or  less  changed  conditions  in 
different  ways  upon  different  parts  of  the  variable  organism 
during  the  great  period  of  time  necessary  to  accomplish  this 
dispersion.  Bdellostoma  has  been  widely  distributed,  and 
while  the  conditions  in  different  parts  of  the  territory  which  it 
inhabits  can  hardly  be  held  to  be  identical,  still  the  sea  bottom 
is  far  more  stable  in  its  temperature  and  other  features  produc- 


154  BIOLOGICAL   LECTURES. 

tive  of  variation  than  the  shallower  waters  of  inland  basins  or 
the  surface  of  the  land  itself.  Hence  so  far  as  the  effects  of 
geographical  distribution  are  concerned,  they  may  be  said  to  have 
had  very  little  or  almost  no  effect  npon  the  anatomical  structui'e 
of  the  animal.  This  conclusion  is  fully  sustained  by  the  fact 
that  in  each  locality  Bdellostoma  shows  similar  variability  in 
the  same  organs,  while  individuals  from  widely  separated 
localities  show  variations  which  are  frequently  numerically 
identical.  The  variability  is  of  the  same  kind  and  comparable  in 
degree  ia  individuals  from  all  the  localities  yet  studied.  This 
is  by  no  means  a  satisfactory  presentation  of  the  effect  of 
geographical  distribution,  but  it  must  suffice  for  the  present, 
and  until  our  knowledge  of  the  distribution  of  the  animal  has 
been  more  fully  elucidated. 

What  effect  should  these  facts  have  upon  our  ideas  of  the 
classification  of  Bdellostoma.'*  Most  authorities  are  inclined  to 
look  upon  the  difference  in  the  number  of  gills  as  a  sufficient 
ground  for  the  establishment  of  distinct  genera.  That  this 
character  has  not  a  generic  value  it  is  needless  to  state,  for 
reasons  already  sufficiently  repeated.  But  it  would  be  conven- 
ient to  recognize  these  several  varieties  by  some  name,  if 
possible,  and,  according  to  the  present  system  of  nomenclature, 
there  are  two  opportunities,  —  one  for  a  specific,  the  other 
for  a  variety  name.  Is  the  gill  variation  a  sufficient  specific 
character }  I  think  not,  for  the  reason  that  we  have  all 
grades  of  the  variations,  and  the  further  reason  that  they  all 
belong  to  one  colony  of  freely  intercrossing  individuals.  It 
appears  to  me  by  far  the  best  plan  to  recognize  one  genus 
of  Bdellostomids,  with  one  species  composed  of  the  several 
varieties,  and  I  propose  that  we  return  to  the  first  satisfactory 
name  that  was  applied  to  our  animal.  The  first  account  of 
this  animal  which  we  find  in  the  literature  is  that  of  Lacepede, 
who  described  it  from  a  dried  skin  sent  from  the  Chilian  coast. 
He  named  it  le  GastrobrancJie  dombey}  Later,  in  1815,  Home 
described  the  gills  of  a  Heptatrema  which  he  obtained  from 

1  Gaetrobranchus  is  the  old  name  applied  to  Myxine,  and  these  forms  were  kept 
with  Myxine  till  Dumeril  put  them  in  the  genus  Heptatrema,  which  of  course 
gives  this  name  priority  over  Miiller's  Bdellostoma. 


BDELLOSTOMA    DOMBEYI,    LAC.  155 

Banks'  South  Sea  collection.  Johannes  Miiller  published  his 
well-known  monograph  on  these  forms  in  1834,  and  applied 
the  name  Bdellostoma  to  the  forms  from  the  South  Sea, 
Cape  of  Good  Hope,  and  Chilian  coast,  making  species  on 
the  basis  of  the  number  of  gills.  He  called  the  Chilian  form 
B.  dombeyi,  and  made  five  species  in  all.  In  1854,  C.  Girard 
described  a  fish  from  the  Chilian  coast  with  fourteen  gills,  and 
called  it  Bdellostoma  polytrema. 

In  1878,  Lockington  described  the  form  found  in  San 
Francisco  Bay  as  B.  stouti,  and  Gill  changed  the  name  in 
1880  to  Polistotrema  stouti,  which  has  again  been  changed  to 
Polistotrema  dombeyi.  Retaining  the  name  polytrema  for  the 
Chilian  form,  he  changed  it  over  to  his  genus  Polistotrema, 
which  he  says  is  characterized  by  1 1  to  14  gills.  These 
accounts  all  refer  to  the  varieties  of  what  I  shall  call  Bdello- 
stoma dombeyi,  adopting  Miiller's  genus,  on  account  of  the 
inapplicability  of  Lacepede's  Gastrobranchus,  and  of  the  inap- 
propriateness  of  Cuvier's  Heptatremes,  which  could  only  be 
used  for  the  seven-gilled  form  or  variety.  Bdellostoma,  the 
generic  name  proposed  by  Miiller,  is  satisfactory  in  every  way, 
and  we  may  well  use  it. 

The  specific  name  dombeyi,  applied  by  Lacepede  in  1798,  is 
satisfactory  in  that  it  avoids  all  difficulties  of  a  morphological 
kind,  and  perpetuates  the  name  of  the  discoverer  of  this 
remarkable  animal.  Bdellostoma  dombeyi  is  the  name  under 
which  are  gathered  all  the  variations  we  know  of  in  the 
branchial  and  dental  systems  and  the  correlated  organs.  F'or 
the  purpose .  of  distinguishing  these  varieties,  we  may  use 
either  Latin  variety  names  or  a  simpler  numerical  termination. 
If  we  choose  the  Latin  names,  we  meet  with  difficulty  in  sup- 
plying all  of  the  Jictci'otrcmes  with  sufficiently  exact  names,  for 
some  are  6-^,  others  11-12,  and  still  others  12-13-gilled,  and 
no  one  knows  when  or  where  more  of  these  heterotrem.es  may 
be  found. 

Gastrobranchus  dombeyi  (Lacepede),   1798. 
Heptatremes  dombeyi  (Cuvier),   1829. 
Bdellostoma         "  (Miiller),   1834. 

(Gray),   1851. 


156  BIOLOGICAL   LECTURES. 

Bdellostoma   polytrema  (Girard),   1854. 

"  "  (Giinther),   1870. 

"  "  (Putnam),   1874. 

"  Stoutii   (Lockington),   1878. 

Polistotrema  dombeyi  (Gill),  188 1. 

(Jordan,  Gilbert),   1882. 
IMellostoma  forsteri.     / 

"  cirrhatus.  * 

"  hexatrema. 

•'  heterotrema. 

"  heptatrema. 

I  shaU,  for  my  own  convenience,  hereafter  use  the  numerical 
method  of  designating  the  varieties  ;  and,  unless  sufficient 
reasons  be  brought  against  this  style  of  name,  I  would  urge 
its  adoption  on  the  ground  of  convenience,  to  go  no  further. 

Iklellostoma  dombeyi,  6  gills. 

"  "         6-7.  )     Indicating   the  sides   of  the   body  upon 

"  "         ']-(i.  S        which  the  respective  numbers  occur. 

7. 
"  10. 

"  "  II. 

"  "  11-12. 

"  "  12-11. 

"  "  12. 

12-13. 

13-12. 

13- 

14. 

Physiological. 

From  previous  experience  it  seemed  to  me  very  desirable 
that  physiological  experiments  should  be  tried  upon  the  ear 
of  some  vertebrate  with  the  simplest  existing  type,  and,  if 
possible,  upon  an  animal  which  lacked  fins,  —  /.  ^.,  paired 
appendages,  which  in  all  fishes  are  specially  used  in  main- 
taining the  equilibrium  of  the  body.  I  felt  that  by  securing 
these  conditions,  we  should  be  able  to  get  much  cleaner 
responses  or,  in  any  case,  safer  results  from  operations  on 
the  ear,  for  the  presence  of  the  paired  fins  —  especially  the 
pectoral  fins  —  complicates  the  reaction  to  ear  operations  by 
introducing  into  observable  phenomena  mechanical  factors 
whose  influences  have  not  been  carefully  enough  studied  and 


BDELLOSTOMA    DOMBEV/,    LAC.  157 

allowed  for.  The  desired  vertebrate  was  found  in  Bdellostoma, 
which  thus  presented  me  with  material  for  both  morphological 
and  physiological  investigations.  Physiological  operations  on 
the  ear  of  Cyclostomes  have  been  tried  on  Petromyzon  only,  so 
far  as  I  know,  and  then  they  were  abandoned  without  obtain- 
ing results,  on  account  of  the  difficulty  of  the  operations.  The 
first  operations  I  performed  were  on  anaesthetized  animals  ;  but 
I  soon  abandoned  the  use  of  anaesthetics  for  several  very 
sufficient  reasons. 

My  method  of  operation  was  the  following  :  In  order  to 
hold  the  extremely  slimy  and  slippery  animal,  I  used  large 
sheets  of  blotting-paper,  such  as  botanists  require  for  drying 
plants.  Bdellostoma  was  taken  from  the  aquarium,  and  at 
once  rolled  up  in  the  sheet  in  such  a  fashion  as  to  hold  it 
extended  during  the  operation.  One  sheet  makes  a  roll  suffi- 
ciently stiff  to  retain  the  fish  perfectly.  A  stout  needle  was 
thrust  through  the  skin  at  the  side  of  the  mouth,  and  another 
through  the  skin  and  muscles  of  the  tail,  and  both  forced  into 
the  table  at  such  a  distance  apart  as  to  prevent  the  fish  from 
squirming  or  crawling  out  of  the  paper  cylinder.  The  blotting- 
paper  was  removed  over  the  region  of  the  ear,  and  an  incision 
made  through  skin  and  muscle,  exposing  the  cartilaginous 
ear  capsule.  The  top  of  this  was  shaved  off  with  a  sharp 
scalpel  of  suitable  shape  and  size,  and  the  auditory  nerves 
cut  inside  the  ear  capsule,  either  with  a  scalpel  or  scissors. 
The  columella  was  then  cut,  and  the  ear  lifted  out  with 
forceps  or  with  a  small  bent  needle.  An  examination  was 
made  with  a  lens  to  see  if  any  part  of  the  ear  or  auditory 
nerve  had  been  left  in  the  capsule,  and  any  such  fragments 
were  removed  before  the  cut  in  the  skin  was  sewed  up.  This 
done  the  animal  was  unrolled  into  the  aquarium,  and  its 
motions  watched.  The  whole  operation  does  not  require  more 
than  two  minutes,  and  the  fish  does  not  appear  to  suffer  in  the 
least  from  suspended  respiration,  so  far  as  I  could  make  out. 

A  fish  thus  operated  upon,  with  both  cars  removed,  will 
swim  from  the  moment  it  is  placed  in  the  aquarium  like  a 
normal  fish.  In  some  cases  the  creature  will  tie  itself  into 
a  knot,   with  the  evident  ]:)urpose  of   removing   the  irritation 


158  BIOLOGICAL   LECTURES. 

from  the  skin  of  the  head,  but  it  soon  leaves  off  such  attempts, 
and  settles  down  on  the  bottom  of  the  aquarium,  coiling  up  in 
the  normal  fashion,  or  else  it  will  continue  to  swim  about  the 
tank  for  a  time.  In  case  only  one  ear  is  taken  out,  the  animal 
may  (it  does  not  always  do  so)  swim  with  the  injured  side 
lower  than  the  other,  or  may  even  roll  as  it  swims  —  especially 
if  it  is  excited  to  szoim  rapidly ;  but  like  others,  it  will  settle 
to  the  bottom,  and  rest  normally  in  its  coil,  coiling  either  away 
from  or  toward  the  injured  side.  I  thought  I  could  notice  in 
some  cases  a  tendency  to  coil  away  from  the  injured  side  ;  i.e., 
the  norn#il  side  did  the  work  of  coiling  ;  but  the  case  is  by  no 
means   clear   that   this   coil    is   done   oftener   than   the   other. 


Fig.  14. — The  right  internal  ear  of  the  Hagfish 
{Myxine  gluiinosa),  seen  from  the  inside  or  cerebral 
face.  P^igure  after  G.  Retzius.  The  figure  represents 
the  ear  somewhat  enlarged,  and  does  not  show  the 
shape  or  exact  positions  of  the  contained  sense- 
organs. 

a       Anterior  ampulla.  d       Ductus  endolymphaticus. 

ap    Posterior  ampulla.  fnu    Macula  utriculi  et  sacculi. 

c       Anterior  and  posterior  canals.  ;/       Nerve  branchlets. 

ca  )   .  -.^  1      r  .1  "       Utriculo-sacculus. 

\  Ampullar  ends  of  the  same. 
^r  )  s        Sacculus  endolymphaticus. 

Now,  on  the  hypothesis  that  the  ear  is  the  specific  organ  of 
the  equilibrative  sense,  it  might  be  argued  that  the  removal 
of  one  ear  does  not  necessarily  so  powerfully  affect  the  equi- 
librium of  the  body  as  to  destroy  even  the  control  of  the 
injured  side  ;  for  the  uninjured  side  is  able  to  take  upon  itself 
the  functions  of  the  injured  organ  in  part  at  least.  If  that 
were  the  case,  when  both  ears  were  removed  we  should  cer- 
tainly expect  to  see  the  animal  lose  control  of  its  body  ;  but, 
as  I  have  already  said,  the  animal  is  even  better  off  zvith  both 
ears  removed  than  with  one  ear  removed,  for  all  traces  of  equi- 
librative distiirbaiice  disappear  at  once  on  the  removal  of  the 
second  ear. 

How  can  the  semi-circular  canal  with  its  two  ampullae  be 
the  special  organ  of  dynamical  equilibrium  and  the  utriculo 
sacculus  with   its   sense  organs   the   special  organ  of  statical 


BDELLOSTOMA    BOMB E VI,    LAC.  I  59 

equilibrium  when  the  animal  maintains  its  perfect  equipoise 
without  them?  If  in  higher  forms  each  canal  appreciates 
movements  in  its  own  plane  and  by  definite  functional  combi- 
nations of  two  or  more  canals  is  able  to  mediate  all  possible 
rotational  movements,  what  function  has  the  single  canal  in 
Myxime,  or  the  two  canals  in  Petromyzon  ?  Both  of  these 
creatures  are  subject  to  the  same  mechanical  conditions  in  their 
progress  through  the  water  that  the  higher  vertebrates  are. 
The  fact  that  they  do  not  have  the  canals  proves  that  vertebrates 
can  swim  as  admirably  without  this  apparatus  as  with  it,  and 
such  being  the  case,  what  was  the  physiological  incentive 
which  lead  to  the  production  of  the  other  canals  ?  I  have 
elsewhere  given  a  sufficient  mechanical  explanation  of  the 
genesis  of  the  canals,  but  I  have  yet  to  learn  of  a  sufficient 
physiological  one.  Who  will  add  to  our  knowledge  in  this 
particular? 

It  is  said  that  the  semi-circular  canals  in  man,  for  example, 
are  delicate  organs  whose  special  function  is  to  take  cognizance 
of  all  the  motions  of  the  body  in  their  respective  planes,  and 
that  they  thus  control  either  singly  or  by  various  combinations 
with  the  other  canals  of  the  opposite  side  of  the  body,  all 
possible  movements  of  the  body. 

One  may  readily  disprove  this  assumption  by  a  very  simple 
experiment.  Have  some  person  with  normal  ears  and  normally 
developed  muscles  swim  for  a  distance  on  his  back  with  closed 
eyes  —  first  with  his  hands  and  arms  alone,  keeping  his  legs 
straight,  and  second  with  his  feet  alone,  folding  his  arms  on  his 
breast.  The  average  man  is  stronger  on  the  right  side  of  his 
body  than  on  the  left,  and  consequently  when  he  pulls  himself 
through  the  water  with  his  arms  alone  —  eyes  closed  —  he 
unconsciously  pulls  himself  to  the  right  and  swims  in  a  circle 
—  {Rcitba/ui  bcivcguiigcii  of  German  pJiysiologists  I)  When  he 
swims  with  his  feet  alone  he  pushes  himself  through  the  water 
and  consequently  pushes  himself  over  to  the  left  side  and 
swims  in  a  circle  in  an  opposite  direction  to  what  he  did  before 
{fij'ciis  i}iovci)icnt  to  tJic  left!)  and  he  is,  so  long  as  his  eyes 
remain  closed,  unconscious  of  the  fact  that  he  is  moving  to 
one  side  i.e.,  diverging  from  a  straight  line  —  but  he  becomes 


l6o  BIOLOGICAL   LECTURES. 

conscious  of  this  fact  the  moment  his  eyes  rest  upon  some- 
thing which  enables  him  to  orient  himself,  and  yet  this  normal 
individual  has  six  organs  in  his  head  which  are  there  for 
the  special  purpose  of  controlling  of  his  movements  in  space, 
so  say  the  physiologists.  His  two  eyes  are  of  more  service  to 
him  than  are  his  six  canals.^ 

It  may  be  objected  that  the  canals  are  not  intended  to  take 
cognizance  of  such  minute  changes  in  position  in  space  as  are 
involved  in  swimming  around  in  a  circle;  but  if  they  cannot 
perceive  such  changes  of  position  when  swimming,  how  can 
they  perceive  them  when  on  a  rotating  table  {e.g.,  Crum. 
Brown's  experiment).  It  would  be  a  great  service  to  determine 
the  minimum  amount  of  angular  motion  of  which  the  canals 
can  take  cognizance,  in  order  that  we  may  know  how  much  to 
expect  of  our  ear  canals  in  this  way. 

It  may  be  objected  that  the  man  in  the  water  on  his  back  is 
in  an  unusual  position  and  consequently  his  canals  do  not  work 
with  sufficient  delicacy  on  account  of  the  unaccustomed 
pressure,  etc.  But  it  is  a  necessary  consequence  of  the 
assumption  that  the  canals  are  special  organs  of  equilibrium, 
that  they  should  work  in  any  position;  otherwise  what  were 
the  use  of  them  }  Other  organs  of  specific  function  work  in 
all  positions  of  the  body.  The  eyes  see,  the  nose  smells,  the 
ears  hear,  the  brain  thinks,  the  heart  beats,  and  so  on  ad 
infinitum,  all  except  the  ear  canals,  whose  special  work  is  to 
cognize  just  such  unusual  spatial  conditions,  and  according  to 
the  hypothesis,  the  only  organs  in  the  body  having  this 
function, — they  fail  of  their  function  when  most  needed.  In 
the  experiment  with  the  rotating  table  the  canals  are  subject 
to  even  a  severer  test  of  very  small  angular  motion  and  are 
supposed  to  be  able  to  operate  very  precisely,  in   some  cases. 

1  Experimental  rides  on  the  great  Ferris  wheel  at  Chicago  during  the  Columbian 
Exposition  proved  that  a  perception  of  the  direction  of  the  motion  of  one's  body 
in  space  was  impossible  unless  one  made  use  of  the  eyes.  I  found  that  the 
upward  motion  could  not  be  detected  by  the  ears  alone.  Without  the  evidence 
of  one's  eyes  one  seemed  to  be  standing  still  upon  a  trembling  platform,  and  the 
while  was  really  making  a  great  circle  through  the  air  in  a  geotropically  oriented 
position.  It  is  notorious  that  balloonists  have  difficulty  in  determining  whether 
they  are  moving  upward  or  in  any  other  direction  when  sight  is  hindered,  and 
that  it  is  impossible  to  detect  motion  in  the  midst  of  a  cloud. 


BDELLOSTOMA    DOMBEYI,    LAC.  i6l 

I  think  this  swimming  experiment  gives  very  satisfactory 
evidence  to  the  effect  that  the  serni-circular  canals  in  man  do 
not  function  as  organs  of  dynamical  equilibration.  At  the 
opposite  end  of  the  scale  —  Bdellostoma  is  certainly  not 
dependent  upon  its  ear  for  the  equilibrium  of  its  body.  I  may 
say  in  conclusion  that  I  think  Professor  Ewald  has  made  a 
great  discovery  in  showing  how  intimately  the  auditory  nerve 
is  related  to  the  musculature  of  the  body  and  in  proving  that 
some  of  the  complicated  phenomena  which  follow  section  of 
this  nerve  and  of  its  branches  are  fully  accounted  for  by  the 
fact  of  the  lessened  muscular  tonicity  of  the  injured  side  and 
not  on  the  ground  that  these  phenomena  indicate  the  special 
functions  of  the  several  parts  of  the  ear. 


EIGHTH   LECTURE. 


THE    INFLUENCE    OF    EXTERNAL   CONDITIONS 
ON   PLANT   LIFE. 

W.  p.  WILSON. 

If  you  open  your  eyes  and  look  carefully  about,  as  you  are 
traveling  from  place  to  place,  you  will  easily  see  that  there 
are  very  many  differences  between  the  plants  of  one  region 
and  those  of  another.  In  the  high  mountains  you  will  find 
many  thick -leaved  plants,  such  as  the  Rhododendrons  and 
Sedums,  and  quite  a  number  of  peculiar  forms  not  seen  lower 
down.  Many  of  these  may  have  a  stunted,  gnarly  or  dwarfed 
look,  quite  strange  to  the  vegetation  at  the  sea  level.  In  still 
another  region  the  plants  may  have  lost  much  of  their  natural 
grace  and  beauty  of  form.  They  may  look  rigid  and  stiff,  with 
small  thickened  leaves  or  none,  with  short  thickened  stems,  or 
round  and  consolidated  forms  such  as  we  find  in  the  Cacti  or 
Euphorbias.     These  are  the  tenants  of  desert  regions. 

Again,  if  you  happen  to  go  south  into  the  tropics,  sheltered 
and  shaded  by  immense  thin-leaved  trees,  with  the  waving 
green  of  the  palm  and  the  vine,  you  will  find  dense  masses 
and  banks  of  dark  green  foliage  belonging  to  Ferns  and  Sella- 
ginellas,  with  climbing  plants  of  various  kinds  intermingled. 

About  your  own  door  may  be  quite  as  interesting  forms  as 
in  more  remote  districts,  only  you  are  accustomed  to  them  and 
do  not  see  their  peculiarities.  You  may  look  out  on  pines  and 
oaks,  on  a  great  diversity  of  small  plants,  with  the  Indian. pipe, 
a  partial  parasite,  and  a  few  ferns  which  can  bear  more  wind 
and  cold  than  most  of  their  relatives,  plenty  of  mosses  and 
lichens,  and,  in  fact,  representatives  of  all  the  great  plant 
families. 


1 64  BIOLOGICAL   LECTURES. 

The  ancients  looked  upon  the  whole  animate  world  as  having 
been  directly  created  by  some  higher  power,  and  believed  that 
each  species  indicated  a  distinct  and  individual  creation.  They 
also  observed  #iese  differences  between  the  plants  of  different 
regions,  and,  in  fact,  between  those  of  the  same  region.  They 
thought  that  all  living  organisms  were  created  to  fit  the 
special  location  and  conditions  under  which  they  existed. 
They  believed  that  water  animals  and  water  plants,  for 
example,  had  always  been  and  would  always  remain  such  ; 
that  the  desert  region  had  always  been  a  desert  region,  and 
that  the  Cactus  had  been  created  to  fit  it.  We  are  not 
obliged  to  go  very  far  back  in  the  history  of  our  own  times 
to  find  eminent  naturalists  who  have  strongly  advocated  this 
view.  No  less  a  man  than  Louis  Agassiz  was  one  of  the 
most  strenuous  defenders  of  this  theory.  He  believed  that 
species  of  both  plants  and  animals  were  invariable,  living 
and  dying  in  form  and  color  and  habit  just  as  they  were 
created.  And  there  were  many  other  naturalists  the  world 
over  who  held  to  this  doctrine  of  special  creation.  It  must 
not  be  forgotten,  however,  that  though  their  views  attained 
no  prominence,  such  men  as  Lamarck  had  at  different  times 
indicated  a  strong  belief  in  the  variability  of  forms. 

During  the  last  twenty  years  there  has  been  a  great  revision 
of  thought  in  regard  to  these  subjects.  At  present  all 
naturalists  believe  not  only  in  the  possibility  of  a  continual 
change  in  both  plants  and  animals,  to  fit  them  for  varying 
conditions,  but  also  in  the  gradual  growth  and  development  of 
very  diverse  changes  in  climates,  rendering  equal  modifications 
in  both  fauna  and  flora  absolutely  essential  to  their  continued 
existence.  Since  great  changes  have  always  been  slowly  taking 
place  in  the  earth's  surface  and  climate,  and  since  present 
vegetation  has  always  been  subject  to  these  gradually  varying 
conditions,  it  must  have  adapted  itself,  with  a  slowness  commen- 
surate with  the  earth's  changes,  to  the  ever-appearing  new 
conditions.  In  this  way,  we  think,  can  be  solved  the  problem 
of  the  infinite  variety  of  vegetation. 

By  experiment  we  may  determine  the  two  factors  underlying 
plant  variation.     On  the  one  hand  the  laws  of  inheritance  are 


EXTERNAL    CONDITIONS   ON  PLANT  LIFE.  1 65 

ever  holding  the  plant  invariable,  while  the  external  forces 
are  ever  pushing  it  toward  variation.  In  this  lecture  we 
will  disregard  entirely  the  interesting  phenomena  which  relate 
to  that  internal  force  the  manifestations  of  which  we  call 
inheritance,  and  try  to  discover  how  much  the  plant  world  is 
moulded  and  shaped  by  what  is  exterior  to  it. 

If  you  are  inclined  to  think  about  all  these  differences  in 
the  vegetation  of  the  many  regions  through  which  you  have 
travelled  you  will  soon  see  that  where  there  is  great  change 
in  the  appearance  of  the  plants,  in  passing  from  one  place  to 
another,  there  is  also  an  equally  marked  difference  in  the 
surroundings  or  soil  or  climate.  You  will  soon  find  yourself 
always  looking  for  the  one  when  you  have  found  an  expression 
of  the  other,  i.e.,  if  the  plants  give  you  a  new  flora,  you  seek 
at  once  to  find  the  cause  in  external  conditions  ;  or,  if  you 
have  great  external  difference  in  surroundings  and  climate,  you 
expect  this  to  be  at  once  reflected  in  the  varying  vegetation 
about  you. 

Let  us  study  a  few  plants  a  little  more  closely,  and  see 
if  we  are  able  to  determine  on  what  this  variation  depends 
and  how  rapidly  it  may  take  place.  I  shall  assume  at  the 
outset  two  sets  of  causes,  both  of  which  may  be  active  in 
bringing  about  variations  in  plants,  the  one  wholly  external, 
such  as  light,  heat,  moisture  and  the  like,  and  the  other 
internal,  and  concerned  with  the  laws  of  inheritance,  about 
which  we  know  so  very  little. 

Let  us  for  our  present  purpose  consider  only  the  external 
influencing  conditions,  for  I  believe  that  they  are  much  more 
potent  and  determinative  than  the  laws  of  inheritance.  They 
may  be  enumerated  as  follows  : 

I.  The  Water  Supply. —  This  is  more  important  than  any  of 
the  following  points,  as  it  is  intimately  connected  with  the 
very  vital  process  of  organizing  materials  for  growth  and 
their  transport  throughout  the  plant. 

If  the  water  supply  is  cramped  and  too  little,  we  have 
immediately  before  our  minds  the  desert  plants. 

If  the  water  supply  is  too  great,  equally  important  changes 
take  place. 


1 66  BIOLOGICAL   LECTURES, 

2.  The  Light  Supply — Here   again  we    may  have    too    much 

or  too  little,  either  condition  leaving  its  strong  impress 
on  the  plant. 

3.  Altitude  i#a  third  factor  in  the  growth  of   plants,  which 

strongly  influences  the  light,  the  moisture  and  the  tempera- 
ture, as  we  shall  see  in  a  later  discussion. 

4.  Temperattif-e. —  Temperature    and    light,    together,    govern 

largely  the  transpiration  of  water  from  the  plant. 
The  character  and  position  of  the  leaves  are  often  wholly 
adapted  to  both  the  conservation  and  the  loss  of  water  by 
transpiration. 

5.  The  Food  Supply  produces  the  most  fundamental  changes 

in  the  life  of  the  plant,  strongly  influencing  not  only  the 
production  and  character  of  the  flower  and  the  fruit,  but 
in  all  probability  determining  the  sex  itself. 

6.  The  Lnfltience  of  the   Sea   upon  Plant  Forms. —  It  will   be 

seen  that  quite  as  remarkable  changes  come  to  the  sea  as 

to   the   desert   plants,   and   in   truth    based    upon    similar 

reasons. 

(i)   Let  us  first  consider  the  water  supply.     You  will  readily 

bring  before  the  mind's  eye  the  picture  of  desert  plants,  which 

represent  in  their  modifications  a  lack  of  water.      But  you  will 

not  so  easily  call  to  remembrance  plants  which  have  undergone 

changes  from  an  oversupply  of  water.     Yet  there  are  many  of 

them   even  in  your  own  neighborhood. 

The  Bald  Cypress  {Taxodimn  disticJinm)  grew  in  the  present 
Arctic  region  before  the  Glacial  Epoch,  in  company  with  oaks, 
maples,  willows,  the  Redwoods  {Sequoia  gigantea,  S.  semper- 
virens),  the  Gingko  tree  (Salisdnria  adianti/olia),  Torreya,  and 
Glyptostrobns.  During  later  changes  in  climate  these  trees 
were  driven  from  their  home  and  travelled  down  widely  different 
lines  into  the  South.  For  reasons  which  we  are  unable  to 
understand,  the  Sequoia,  or  Redwood,  descended  along  the 
California  coast,  the  Glyptostrobns  and  the  Salisburia  or  Gingko 
tree,  down  the  coasts  of  China  and  Japan,  the  Torreya  and 
Taxodimn,  or  Cypress,  to  the  eastern  and  southern  parts 
of  North  America.  At  present  the  Bald  Cypress,  to  which  I 
wish  especially  to  call  attention,  grows  only  along  the  water- 


EXTERNAL    CONDITIONS   ON  PLANT  LIFE.  167 

courses  and  in  the  swamps  of  the  south-eastern  part  of  the 
United  States.  It  seeds  itself  naturally  nowhere  outside  of 
areas  which  are  for  several  months  during  the  year  under  water. 
This  tree  belongs  to  the  Pine  family,  but  has  some  very  marked 
peculiarities  which  make  it  differ  strongly  from  any  of  its 
relatives. 

The  tree  shown  in  Plate  No.  i  stands  normally  surrounded 
by  water.  Many  root-like  projections  are  seen  underneath  and 
around  the  tree,  which  are  popularly  known  as  cypress  knees. 
These  are  all  connected  with  the  root  system  below  the  water. 
They  have  extended  their  growth  upwards  until  they  are  sure 
to  remain  in  the  air  at  the  ordinary  level  of  the  water  during 
most  of  the  year.  They  are  in  such  numbers  that  wagon-loads 
of  them  could  be  taken  away  from  one  tree.  P'rom  many 
careful  experiments  made  on  the  growing  seedlings,  it  has  been 
determined  without  doubt  that  these  knees  are  organs  of 
respiration.  All  dry-land  trees  secure  free  oxygen  from  the  soil 
to  carry  on  the  oxidations  needed  in  root  growth.  This  tree 
growing  in  water,  which  holds  much  less  oxygen  than  the  soil, 
is  unable  to  draw  its  full  supply  from  the  medium  surrounding 
the  roots.  To  fill  this  want,  these  knees  are  pushed  up  out  of 
the  water  into  the  air  as  aerating  organs.  Although  the  plant 
does  not  now  grow  normally  on  dry  land,  yet  when  planted 
there  it  thrives  as  it  once  did  in  previous  geologic  ages  in  the 
Arctic  regions.  Plant  two  sets  of  seedlings,  the  one  in  dry 
soil,  the  other  in  soil  flooded  with  water  ;  the  first  will  show  no 
signs  of  the  root-aerating  organs,  while  the  second  will  develop 
them  in  abundance,  as  small  vertical  roots  pushed  above  the 
surface  of  the  water. 

In  the  water  growth,  the  branches  of  the  Cypress  are 
spreading  and  the  top  flattened,  a  marked  departure  from  the 
most  striking  characteristic  of  the  Pine  family,  to  which  it 
belongs.  When  grown,  however,  in  dry  soil,  in  our  parks 
and  public  grounds,  it  reverts  to  the  normal  type.  The 
branches  are  short  and  make  a  sharp  angle  with  the  main 
stem,  and  its  cone-like  form  is  as  pointed  as  in  any  of 
the  tall  conifers.  This  will  be  seen  in  Plate  No.  2,  photo- 
graphed from  a  tree  planted  in  Fairmount  Park,  Philadelphia. 


1 68  BIOLOGICAL   LECTURES. 

It  will  be  observed,  too,  that  there  are  no  signs  of  knees 
underneath. 

Plate  No.  I  represents  a  water  form  from  the  James  River. 
The  ba^,  in  this  form,  is  always  very  much  enlarged.  This 
enlargement  is  a  part  of  the  aerating  system  needed  to  secure 
the  necessary  oxygen,  and  is,  of  course,  entirely  absent  from 
the  land  form. 

The  departure  from  the  sharp,  cone-like  form  natural  to  the 
conifers,  is  due  to  the  difficulty  in  obtaining  both  air  and  food 
from  the  water.  This  lack  of  nourishment  shows  itself  in  the 
dwindling,  depauperate  and  dying  branches  of  the  upper  part, 
since  that  part  is  most  remote  from  the  food  supply. 

In  some  of  the  lakes  of  Southern  Florida  it  now  and  then 
happens  that  a  cypress  tree  has  obtained  a  foothold  in  much 
deeper  water  than  is  its  normal  habit.  Here  all  of  these  water 
peculiarities  are  greatly  exaggerated.  The  trunk  of  the  tree 
produces  an  immense  cone,  the  top  of  which  points  up  to  the 
surface  of  the  water  and  ends  with  a  few  flat  sprayey  branches. 
The  base  of  the  cone  may  be  forty  or  fifty  times  the  diameter 
of  the  top,  from  which  come  the  few  straggling  branches  which 
project  above  the  surface  of  the  water.  There  are  at  its  base 
innumerable  knees.  In  a  tree  having  the  height  of  twenty- 
five  or  thirty  feet,  the  cone  below  the  water  will  represent  a 
little  over  one-half,  and  the  branches  above  the  other  half  of  its 
altitude.  Plate  No.  3  represents  such  a  tree  in  South  Florida 
after  the  waters  of  the  lake  had  been  drained  away.  The 
knees,  being  of  no  further  use,  quickly  rotted  .and  disappeared 
and  are  not  shown  in  the  photograph.  Originally  the  water 
was  high  enough  to  touch  the  lower  branches,  and  the  tree 
eked  out  a  miserable  existence,  struggling  hard  in  the  deep 
water  for  both  air  and  food.  The  difficulties  under  which 
it  labored  developed  it  into  a  great  monstrosity.  It  is  an 
extreme  expression  of  excessive  water  supply.  Compare  its 
short,  cone-like  trunk,  entirely  immersed  in  water,  with  what 
may  be  called  the  normal  development  now  found  only  in 
our  parks  (Plate  No.  2).  In  this  form  the  trunk  is  tall  and 
slender,  with  branches  towering  to  a  very  sharp  point.  The 
water    form    has    acquired    its    knees    and    greatly    enlarged 


No.  1.  —  TAXODIUM    DISTICHUM    RICH.— JAMES    RlVER,   V'A. 


NO.  2.— TAXODIUM   DISTICHUM    RICH.  —  FAIRMOUNT   PARK,   PHILA. 


EXTERNAL    CONDITIONS   ON  PLANT  LIFE.  169 

base  for  jxirposes  of  respiration.  Its  flattened  cone  is  the 
result  of  the  bad  nutrition.  The  land  form,  dropping  into  its 
native  dry  earth  habitat,  does  not  develop  the  knees  and 
enlargement,  because  its  oxygen  supply  is  ample.  Its  nourish- 
ment, too,  is  sufficient,  so  that  it  will  have  as  a  result  of  these 
normal,  favorable  conditions,  the  tall,  sharp,  cone-like  form 
natural  to  the  pine  family.  Doubtless  the  cypress  has  been 
millions  of  years  adapting  itself  from  its  dry  land  conditions 
to  its  watery  surroundings,  and  the  most  interesting  fact  in  this 
connection  is  its  readiness  to  fall  back  into  its  old  habit  of 
growth,  and  even  in  the  first  generation  on  land  to  lose  every 
trace  of  these  wonderful  acquisitions. 

The^e  are  many  other  plants  which  have  acquired  equally 
remarkable  organs  in  the  same  way.  Some  of  the  mangroves 
of  the  Florida  coast  such  as  Aviccnnia  iiitida  and  Laguncularia 
raccnwsa,  growing  in  the  ooze  between  tide- waters,  have  developed 
vertical  roots  which  project  out  of  the  mud  by  hundreds  under 
each  tree  and  are  exposed  to  the  air  at  every  low  tide.  These 
organs  aerate  the  plant  as  the  knees  aerated  the  cypress. 
They  are  much  more  highly  organized,  being  covered  on  the 
parts  above  the  mud  with  great  numbers  of  large,  open 
lenticels. 

It  is  not  necessary  for  us  to  go  so  far  from  home  to  find 
numbers  of  plants  which  have  adapted  themselves,  through 
special  aerating  organs,  to  a  change  from  dry  land  to  water 
growth.  One  of  the  most  common  is  Dccodon  vcrticiiiatiiSy 
which  develops  over  the  surface  of  all  its  roots  an  extremely 
thickened,  corky,  air-holding  layer.  A  similar  development 
covers  the  branches  when  they  happen  to  drop  into  the  water. 

Let  us  now  see  how  plants  are  modified  when  they  lack 
water.  If  the  supply  is  inadequate,  the  plant  makes  an 
attempt  to  conserve  the  little  that  it  has.  As  the  surface  of 
ordinary  plants  allows  large  quantities  of  water  to  escape  by 
transpiration,  and  as  this  loss  is  largely  proportioned  to  the 
amount  of  surface  exposed,  such  plants  usually  lessen  this 
surface  by  making  the  leaves  smaller  and  thicker,  or  by  losing 
them  entirely,  by  shortening  the  branches  and  by  consolida- 
tion generally.      As  the  light  and  the  heat  of  the  sun  increase 


170 


EIOLOGICAL   LECTURES, 


transpiration,  the  surface  of  the  plant  may  become  for  protec- 
tive purposes  hairy;  the  cuticular  and  epidermal  layers  may 
be  thickened;  the  interior  air  passages  in  the  leaf  which 
communicate  with  the  surface  may  become  obliterated  through 
consolidation  of  the  cellular  structure;  and,  in  certain  cases, 
the  leaf  may  have  added  to  it  definite  kinds  of  tissue  for 
storing  water  to  be  used  in  time  of  need. 

(2)  That  light  readily  causes  various  reactions  in  many  of 
our  ordinary  plants,  every  one  knows.    Watch  the  folding  of  the 


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Plate  No. 


I'late  No.  5. 


Clover  leaves  as  daylight  decreases,  and  you  will  see  them  go 
into  their  sleeping  position,  while  in  the  morning  they  open 
their  faces  and  present  them  to  the  sky.  Look  at  the  Wistaria 
vine  by  the  aid  of  a  lamp,  late  at  night,  and  you  will  see  that 
the  little  leaflets  have  dropped  down  and  closed  together.  If 
the  morning  is  bright  and  warm,  they  will  rise  early  and  by 
nine  o'clock  every  young  tender  leaflet  will  point  its  tip  directly 
at  the  sun,  in  a  direction  parallel  with  both  the  light  and  heat 
rays.    As  the  heat  of  the  sun  increases  toward  noon  and  during 


EXTERNAL    CONDITIONS   ON  PLANT  LITE. 


171 


the  hotter  part  of  the  day,  you  will  find  these  leaflets  constantly 
rotating,  maintaining  their  parallelism  to  the  sun's  rays.  If  the 
day  is  cloudy  and  the  heat  of  the  sun  obscured,  these  same 
movable  sensitive  leaflets  may  remain  in  a  stationary  position 
so  as  to  receive  the  most  direct  light  possible  during  the  whole 
day.  If  you  choose  to  wander  in  your  nearest  woods,  many 
similarly-acting  plants  cannot  fail  to  escape  your  notice,  such 


Plate  N<3.  6.  Plate  No.  7. 

as  the  Desmodiumy  the  Lespedcza,  the  Melilotns,  and,  among 
the  tree-like  forms,  Afuorpka,    and  Robinia,  or  the  Locust. 

Plate  No.  4  shows  the  Melilotiis,  or  Sweet  Clover,  on  a  cool, 
moist,  somewhat  cloudy  morning,  when  the  leaves  are  spread 
out  fully,  striving  to  receive  all  the  light  and  warmth  possible. 
The  direction  of  the  light  is  generally  at  right  angles  to  the 
surface  of  the  foliage. 

Plate  No.  5  represents  another  plant  on  an  extremely  hot, 
dry   morning    in   midsummer,    photographed    at    nine   o'clock. 


172 


BIOLOGICAL   LECTURES. 


The  photograph  was  taken  from  the  south.  It  will  be  seen 
that  the  three  leaflets,  elevated  on  their  sensitive  petioles,  are 
all  pointing  directly  at  the  sun  in  the  south-east.  The  leaflets 
being  parallel  to  the  heat  and  light  rays,  escape  much  of  the 
consequent  transpiration  of  water  which  would  occur  were  they 
thrown  down  to  the  sun's  rays  as  in  Plate  No.  4. 

Another  plant,  Plate  No.  6,  photographed  under  similar 
conditions   of   dryness  and   hot  sun  at  twelve  o'clock   in   the 

morning,  shows  the  leaves 
pointing  directly  to  the 
zenith,  thus  again  parallel 
to  the  sun's  rays  and  for 
similar  reasons. 

Plate  No.  7  shows  still 
another  plant  taken  on  the 
same  hot  and  dry  day, 
with  the  leaves  pointing 
directly  toward  the  sun. 
This  photograph  was  taken 
at  2  p.  M.  in  the  afternoon 
from  a  position  15°  north 
of  west,  at  right  angles  to 
a  profile  view  of  the  leaves. 
It  will  be  seen  from 
these  illustrations  that 
when  the  conditions  are 
ripe  for  rapid  loss  of  moist- 
ure, that  these  sensitive 
leaves  continually  keep 
themselves  parallel  with  the  sun's  rays  during  the  day.  As 
the  leaves  in  the  morning  are  first  influenced  by  heat  and 
light,  they  elevate  themselves  and  point  toward  the  eastern 
sun.  They  continue  to  rotate  during  the  day,  so  that  at  noon 
they  are  erect,  slightly  inclined  to  the  south,  and  at  night  are 
directed  to  the  west. 

Plate  No.  8  shows  a  cluster  of  these  plants  photographed 
from  the  north  at  six  o'clock  in  the  afternoon  after  a  compara- 
tively warm,  dry  day.      The  leaves  are  mainly  pointing  to  the 


Plate  No.  8. 


EXTERNAL    CONDITIONS   ON  PLANT  LIFE. 


173 


right  toward  the  western  sun  which  is  still  quite  high.  At 
sundown,  after  the  influence  of  the  falling  dew  has  been  slightly 
felt,  the  leaves  will  begin  to  assume  the  position  seen  in 
Plate  No.  4. 

If  we  continue  to  watch  this  plant  as  darkness  comes  on, 
we  shall  find  all  these  leaflets  dropping  down  slightly,  each 
turning  itself  one-fourth  around  on  its  petiole  until  the  three 
present  their  edges  up- 
permost. The  two  outer 
leaflets,  having  their  faces 
toward  each  other,  move 
slightly  toward  the  cen- 
tral one  until  they  touch 
it.  It  will  be  seen  that 
the  three  little  leaflets 
have  thus  placed  them- 
selves together  in  such  a 
way  as  to  reduce  their 
surface  to  nearly  one- 
third  of  the  original  area. 
This  protects  them  from 
radiation  and  the  loss  of 
much  heat  during  the 
night.  Plate  No.  9  shows 
a  plant  while  sleeping, 
the  photograph  having 
been  taken  at  twelve 
o'clock  midnight. 

But  there  are  other 
effects  of  light  more 
marked  than  these  re- 
actionary movements.  In  ordinary  plant  assimilation,  which 
takes  place  only  under  the  influence  of  light,  the  leaves  are 
generally  the  active  organs.  It  sometimes  happens  that  when 
the  light  becomes  insufficient  for  assimilative  purposes,  certain 
parts  of  the  organ  itself  —  the  leaf  —  become  quickly  atrophied 
or  disappear  entirely.  Thus  the  form  of  the  elm  leaf  has 
gradually  become  oblique  on   account  of  the  shading  of  one 


Plate  No.  9. 


174 


BIOLOGICAL   LECTURES. 


of  its  sides.     This  is  true,  too,  of  the  house  begonia  and  many 
others  of  our  common  plants. 

At  high  altitudes,  where  the  differences  of  light  and  shade 
are  much  more  intense,  these  changes  are  correspondingly 
more  quickly  brought  about.  With  these  external  changes  of 
form  there  are  microscopic  differences  which  are  even  more 
striking.  In  Plate  No.  lo  are  shown  two  cross-sections  of 
leaves  taken  from  the  Mountain  Balsam  (Abies  frascrt)^  a  from 
a  sunny  exposure  and  b  from  the  more  densely  shaded  part  of 
the  tree.  In  Fig.  a  we  have  on  the  upper  part  of  the  leaf  the 
palisade  cells   above,  and  the  more  loosely  arranged  tissues,. 


Fig.  b. 


Plate  No.  io. 


for  assimilation,  below.  About  the  middle  of  the  leaf  is  a 
large  resin  duct.  Fig.  b  is  the  cross-section  of  a  similar 
leaf  from  the  same  tree,  carefully  selected  from  a  point 
underneath  the  heavy  branches  which  the  direct  sunlight  never 
reached.  Above  the  resin  duct,  on  the  upper  side  of  the  leaf, 
are  the  palisade  cells,  much  as  in  a  \  but  the  loosely  arranged 
assimilating  tissue  beneath  the  resin  duct  is  seen  to  be  absent 
in  b.  In  other  words,  the  light  was  not  strong  enough  in  the 
lower  shaded  parts  of  this  tree  for  assimilative  purposes,  and 
in  consequence  these  tissues  have  been  dispensed  with. 

(3)    And  here  let  me  speak  of  the  influence  of  altitude,  which 
affects  not  only  the  light  but  also  the  temperature  and  the  air 


EXTERNAL    CONDITIONS   ON  PLANT  LIFE.  175 

supply.  It  will  be  readily  understood  that  at  any  very  high  alti- 
tude the  amount  of  dust  in  the  air  is  at  a  minimum;  also,  that 
the  greater  the  altitude  the  less  dense  the  atmosphere,  which 
will,  consequently,  contain  less  moisture.  But  as  the  illumina- 
tion of  general  space  depends  wholly  upon  the  refraction  of 
light  from  the  dust  and  particles  of  moisture  in  the  air,  it  will 
be  seen  that  refraction  at  high  altitudes  must  be  at  a  minimum, 
and  that  air  spaces  outside  of  the  direct  line  of  the  rays  of 
light  will  be  much  darker  than  at  lower  altitudes.  The  light 
given  to  shaded  leaves,  then,  at  these  high  altitudes  through 
refraction,  often  proves  too  little  for  the  purposes  of  assimi- 
lation, and  the  assimilating  tissue  consequently  disappears. 

This  shows  the  relation  of  altitude  to  light  and  assimilation. 
But  altitude  is  many-sided  in  its  influences.  Because  we  have 
here  less  dust  and  less  moisture  in  the  air,  the  sun's  rays,  not 
being  refracted  out  of  their  course,  are  much  more  direct.  In 
the  shade,  at  an  elevation  of  seven  thousand  feet,  you  are  too 
cool,  but  step  into  the  sunlight  and  your  upturned  face  will  be 
quickly  burned  by  its  strong,  direct  rays.  These,  same  rays 
burn  the  moisture  rapidly  out  of  mountain  leaves.  To  avoid 
this  as  much  as  possible,  they  become  thickened  in  many  ways, 
often  decrease  in  size,  and  travel  along  the  same  lines 
generally  for  water  retention  as  have  the  desert  plants.  High 
altitudes,  then,  will  produce  desert-like  plants,  as  seen  in  the 
Live-for-evers,  or  Sediirns.  Not  only  are  the  leaves  found 
decreasing  in  size  and  becoming  thickened,  but  in  all  sensitive 
plants  the  movements  are  much  more  rapid. 

Many  plants  which  do  not  have  daily  movements  of  leaves 
to  accommodate  themselves  to  the  light,  still  put  their  young 
leaves,  when  thoroughly  exposed  to  the  sun,  parallel  to  its  rays 
in  the  hottest  part  of  the  day.  Later  in  the  season,  when  the 
epidermal  tissues  are  more  thoroughly  developed  and  the  cuticle 
has  been  fully  thickened,  the  leaves,  thus  becoming  better  able 
to  resist  the  heat  rays,  drop  down  to  a  position  more  or  less  at 
right  angles  to  the  approaching  light.  Select  another  plant  of 
the  same  species,  which  is  thoroughly  shaded  during  the  whole 
day  —  it  may  not  be  twenty  feet  from  the  first  —  and  we  shall 
find  that  the  young  leaves,  as  they  develop  themselves,  at  once 


176 


BIOLOGICAL   LECTURES. 


drop  down  to  a  position  in  which  the  approaching  light  will  be 
at  right  angles  to  their  surfaces.  Plate  No.  1 1  is  a  photograph 
of  Rhododendron  maximum  taken  at  an  altitude  of  over  4000 
feet.  It  developed  itself  entirely  in  the  sunshine.  It  shows 
the  upper,  or  young  leaves,  erected  vertically  upward  until 
they  are  nearly  parallel  with  the  sun's  rays  during  the  hotter 
portion  of  the  day.  The  leaves  below,  which  are  more  or  less 
horizontal,  are  more  than  one  year  old.     At  the  end  of  the 


Plate  No.  ii. 

first  year,  the  upper  leaves,  having  become  tough  and  coria- 
ceous, will  assume  a  position  parallel  to  the  older  ones  below. 

In  Plate  No.  12  is  shown  a  photograph  of  Rhododendron 
catawbiense  at  the  same  altitude,  but  standing  in  a  thoroughly 
shaded  spot.  Although  a  different  species,  the  action  of  the 
leaves  is  the  same.  It  will  be  seen  that  the  young  and  growing 
leaves  above  put  themselves  quickly  in  a  position  parallel  with 
the  leaves  below  during  development. 

The  differences  between  the  microscopic  structures  of  the 
leaves  exposed  to  direct  sunlight  and  of  those  wholly  shaded 


EXTERNAL    CONDITIONS   ON  PLANT  LIFE, 


177 


are  even  more  marked  than  the  corresponding  differences  in 
position.  Plate  No.  13  shows  two  sections  of  leaves  from 
Rhododendron  maximum,  the  one  from  the  sunlight,  the  other 
from  the  shade.  Section  a,  from  the  sun,  shows  four  super- 
imposed rows  of  palisade  cells,  extremely  long  and  narrow, 
arranged  with  their  long  diameters  pointing  to  the  surface  of 
the  leaf  in  a  way  to  afford  the  best  protection  from  the  heat 
rays.  Section  b,  from  the  shade,  has  no  very  well  marked 
palisade  system,  for  no  such  protection  is  needed.     The  section 


Plate  No.  12. 

from  the  sun  is  much  thicker  than  that  from  the  shade,  but 
while  the  loosely  arranged  mesophyll  in  the  under  part  of  the 
leaf,  where  assimilation  is  most  active,  occupies  in  the  sun 
section  only  one-half  of  the  space  of  the  whole  leaf,  yet  in  the 
shade  section  it  includes  more  than  two-thirds.  The  explana- 
tion is  simple.  The  exposed  leaf  requires  less  space  for  the 
work  of  assimilation  on  account  of  the  strong  light.  The  shaded 
leaf,  on  the  contrary,  as  much  less  light  reaches  it,  must  have  a 
greater  number  of  cells  in  which  to  do  a  given  amount  of  work. 
(4)  The  food  supply  of  the  plant  may  exert  a  very  strong 
influence  upon  its  development  and  life.      It  is  a  well-known 


178 


BIOLOGICAL   LECTLJRES. 


fact  among  gardeners  that  over-fed  plants  will  often  produce  no 
fruit.  When  pear-trees  refuse  to  bear  fruit,  they  can  often  be 
made  prolific  by  cutting  away  the  central  root,  thus  lessening 
the  supply  of  nourishment.  As  a  rule,  when  plants  are  poorly 
fed,  they  put  forth  blossoms  and  ripen  their  fruit  earlier, 
although  it  may.  be  smaller  and  of  poorer  quality. 

(5)  The  influence  of  the  sea  upon  plants  is  quite  remark- 
able. We  have  seen  that  in  desert  regions,  and  to  some  extent 
in  high  altitudes,  plants  have  greater  or  less  tendencies  to  take 
on  consolidated  forms.     This  is  also  true  of  seashore  plants. 


caOPQO 


Section  a. 


Plate  No.  13. 


Section  b. 


The  cause  in  both  desert  and  mountain  regions  was  a  lack  of 
moisture.  On  the  seashore,  at  the  water's  edge,  and  even 
with  many  plants  standing  in  the  water,  we  find  these  thick- 
ened leaves  and  leafless  forms.  Hence  we  must  look  for 
another  cause  for  this  than  lack  of  water. 

Ordinary  land  plants  secure  the  water  which  they  need 
mostly  through  their  roots.  Although  the  soil  may  be  appar- 
ently dry,  yet  the  plant  has  no  difficulty  in  supplying  its 
necessities,  for  every  particle  of  the  soil  is  surrounded  by  a 


EXTERNAL    CONDITIONS   ON  PLANT  LIFE.  179 

film  of  water,  which  is  forcibly  taken  from  it  by  the  osmotic 
action  of  the  root  hairs.  Each  hair  is  an  elongation  of  a 
single  epidermal  cell.  Its  external  wall  is  composed  of  porous 
cellulose.  Besides  the  ordinary  cell  contents,  such  as  nucleus, 
masses  of  living  protoplasm,  vacuoles,  microsomata,  and  the 
like,  there  is  a  thin  semi-fluid  layer  of  protoplasm,  closely 
appressed  to  the  whole  interior  of  this  porous  cellulose  wall. 
This  forms,  with  its  cellulose  support,  an  osmometer,  and 
when  the  root  hair  is  tightly  crowded  in  its  growth  against 
the  surrounding  particles  of  earth,  thus  coming  in  contact 
with  the  water  film,  there  is  at  once  set  up,  with  great  force, 
a  current  from  the  thin  fluid  surrounding  the  particles 
through  the  walls  to  the  more  or  less  thickened  one  within. 
Under  a  pressure  often  of  nearly  an  atmosphere,  this  water 
is  forced  from  the  exterior  cells  of  the  root  to  the  interior 
conducting  fibro-vascular  bundles,  through  which  it  finds  its 
way  to  every  part  of  the  plant.  It  will  be  seen  that  the 
condition  of  this  forcible  absorption  is  the  interposition  of 
a  protoplasmic  membrane  between  two  fluids  of  different 
densities,  the  more  dense,  toward  which  the  current  always 
tends,  being  within  the  cell.  It  is  only  necessary  to  state 
that  in  sea-water  we  have  a  fluid  of  even  greater  density 
than  is  usually  found  within  the  cells  of  plants,  and  that 
this  would  tend  at  once  to  make  it  either  very  difficult  or 
utterly  impossible  for  the  plant  to  secure  its  water.  Plants 
which  have  adapted  themselves  to  the  influence  of  sea- water 
have  done  it  in  a  number  of  ways  —  sometimes  by  taking  large 
quantities  of  salt  into  the  cells,  which  balances  much  of  the 
salt  without.  In  this  way  the  density  of  the  fluid  within  is 
made  greater  than  that  of  the  water  without,  and  absorption 
takes  place  to  a  limited  extent.  But  since  it  is  still  very 
difficult  for  the  plant  to  secure  a  large  amount  of  water, 
although  it  may  stand  in  it,  —  "  Water,  water  everywhere,  and 
not  a  drop  to  drink,"  like  Coleridge's  shipwrecked  mariner, — 
all  the  other  methods  of  retaining  its  scanty  supply,  usually 
found  in  desert  plants,  are  here  also  exemplified.  Thus,  the 
leaves  may  become  smaller  or  thickened  or  disappear  alto- 
gether,   in    order   to    lessen  the    transpiring    surface.     If    the 


i8o 


BIOLOGICAL   LECTURES. 


plant  can  get  but  little  moisture,  it  also  retains  that  little,  or 
lets  it  go  with  great  difficulty.  Hence,  we  have  on  the  sea- 
shore a  vegetation  corresponding  in  some  respects  to  that  in 
high  altitudes,  or  to  that  in  desert  regions,  although  the 
apparent  conditions  are  radically  different  from  either. 

Hydrocotyle  iimbellata  is  a  plant  common  in  moist  or  watery 
places  from  Maine  to  Florida.  In  the  semi-tropical  fresh-water 
marshes  of  Florida,  it  places  its  slightly  thickened,  rounded 
leaves  at  right  angles  to  the  sun's  rays,  parallel  to  the  surface 
of  the  water  in  which  it  grows.  When  it  happens  to  encroach 
upon  the  salt-water  marshes  of  this  same  region  the  difficulty 
of  water  supply  is  so  heightened  that  the  slender  petioles 
all    make    a    right-angled    turn   at    their    upper    end  and    put 


Fig.  a 


Plate  No.  14. 


the  now  thickened  leaves  in  a  vertical  position,  in  order  to 
avoid  the  direct  rays  of  the  sun,  thus  lessening  the  loss  of 
water. 

Plate  No.  14.  fig.  a,  shows  a  sketch  of  this  little  plant,  taken 
from  a  fresh-water  stream  in  South  Florida.  Fig.  b  on  the 
same  plate  shows  another  plant  taken  from  a  salt  marsh  near 
by.  All  of  its  leaves  are  rendered  vertical  by  this  turn  in  their 
petioles.  The  microscopic  differences  are  much  greater  than 
this  relative  difference  in  position.  The  leaves  of  the  one  in 
the  salt  marsh  have  become  much  thicker,  the  epidermal  tissues 
much  heavier,  the  number  of  the  palisade  cells  has  increased, 
the    intercellular    spaces    have    nearly    disappeared,    and    the 


EXTERNAL    CONDITIONS   OF  PLANT  LIFE.  i8l 

openings  into  the  stomata  have  been  transformed,  through 
thickening  of  the  cuticle,  into  narrower,  deeper  channels. 
These  differences  are  common  to  many  other  plants  which 
inhabit  indifferently  fresh  and  salt  water  locations. 

The  plants  which  grow  many  miles  from  the  sea-shore  are 
also  more  or  less  influenced  by  the  salt  in  the  spray  which 
is  mechanically  lifted  by  the  winds  and  carried  long  distances 
inland.  Lighting  on  the  leaves,  it  has  a  tendency  to  draw  out 
the  moisture  from  within  and  in  this  way  very  materially 
increases  the  normal  transpiration.  To  guard  against  this 
many  plants  near  the  sea-shore  thicken  up  both  the  cuticular 
and  epidermal  layers.  Where  the  wind  blows  somewhat 
constantly  from  the  sea  over  the  land,  these  effects  may  be 
seen  in  plants  extending  from  the  shore  sometimes  as  far 
as  twenty  miles. 

Many  strand  plants  exhibit  the  same  peculiarities  as  those 
of  the  Rhododendrons  of  the  mountains,  i.  e.^  they  erect  their 
leaves  parallel  with  the  rays  of  the  mid-day  sun  to  avoid  loss  of 
moisture.  This  is  especially  marked  in  the  Mangroves  of  our 
Southern  coast,  which,  for  a  greater  part  of  the  day,  stand 
directly  in  the  water.  The  plants  on  our  New  Jersey  shore 
illustrate  many  of  these  facts  and  are  quite  as  interesting  for 
study  as  those  of  South  Florida.  A  half-dozen  plants  of  one 
of  our  pigweeds  {Atriplex  litt oralis)  taken  from  a  salt  marsh, 
potted,  and  carried  to  a  greenhouse  in  the  city,  exhibited  the 
following  interesting  characteristics:  On  the  salt  marshes  from 
which  they  were  taken,  all  the  leaves  were  rigidly  erect,  making 
no  shadow  with  the  mid-day  sun.  But  after  being  watered  with 
fresh  water  for  five  or  six  days  in  the  greenhouse,  all  of  the 
leaves  dropped  down  to  a  normal  position,  presenting  their 
faces  to  the  direct  rays  of  the  sun.  Upon  watering  them  for 
several  days  following  with  a  strong  salt  solution,  the  leaves 
again  erected  themselves,  assuming  the  precise  position  in 
which  they  had  grown  on  the  salt  marshes. 

It  has  long  been  known,  through  physiological  experimen- 
tation, that  almost  any  salt  or  alkaline  solution  decreases 
transpiration,  because  it  at  once  lessens  the  water  supply.  The 
converse  is  true  of  acid  solutions.     This  law  may  be  taken  as 


1 82  BIOLOGICAL   LECTURES. 

a  partial  explanation  of  the  conduct  of  the  little  New  Jersey 
Pigweed. 

Perhaps  enough  has  been  already  said  to  convince  anyone 
that  the  almost  infinite  variety  of  plant  forms  may  have  some 
fairly  direct  connection  with  their  environment.  The  cypress 
tree  produces  its  needful  aerating  organs  when  grown  in  the 
water,  but  no  sign  of  them  in  dry  soil.  It  may  be  a  matter 
of  wonderment,  however,  why  these  characteristic  organs  are 
so  quickly  and  readily  lost.  They  are  an  acquired  character  to 
fill  a  definite  want  —  when  this  want  no  longer  exists,  they  dis- 
appear. Perhaps  this  character,  which  we  know  was  acquired 
since  the  Eocene  period,  has  endured  for  too  short  a  time 
for  permanent  inheritance.  Many  other  plant  characteristics 
acquired  on  physiological  grounds,  but  regarding  the  duration 
of  which  we  have  no  record,  although  we  have  reason  to 
believe  that  they  have  been  serving  their  purpose  for  an 
immense  period  of  time,  are  perfectly  permanent,  and  inherited 
by  their  offspring  long  after  the  developing  cause  has  disap- 
peared. We  have  in  Australia  a  large  number  of  trees  which 
have  adapted  themselves  to  a  hot  and  dry  climate  by  various 
manipulations  of  the  leaves.  In  some  Acacias,  for  example, 
the  leaf-blade  has  entirely  disappeared,  and  the  wing  growth 
on  the  upper  and  under  sides  of  the  petiole  is  an  apparently 
vertical  leaf.  Other  members  of  the  same  family  make 
the  true  leaf  vertical  by  a  twist  of  the  petiole.  Although 
accomplished  in  two  very  different  ways,  the  object  in  each 
case  is  plainly  to  lessen  the  tranpiration.  Apparently,  this  is 
a  much  more  trivial  change  than  the  acquirement  of  knees  by 
the  Cypress.  Both  fulfil  a  physiological  necessity  ;  but  while 
the  knees  of  the  Cypress  are  lost  in  succeeding  generations 
if  the  developing  cause  is  removed,  the  Acacias  may  be 
cultivated  for  generation  after  generation,  entirely  removed 
from  the  climatic  conditions  which  produced  the  changes,  yet 
they  will  be  as  permanently  inherited  as  in  their  own  native 
land. 

Avicennia  nitida,  the  so-called  Black  Mangrove  of  our 
Florida  and  West  Indies  coast,  of  which  I  have  already  spoken, 
^belongs  to  the  Verbena  family.      Normally  a  dry  land  form,  it 


EXTERNAL    CONDITIONS   OF  PLANT  LIFE.  183 

has  adapted  itself  to  a  growth  between  tide  waters.  In  so 
doing  it  not  only  produces  the  remarkable,  vertical,  negatively 
geotropic  roots,  which  grow  up  out  of  the  salt  mud,  so  that 
at  low  tide  they  remain  each  day  several  hours  in  the  air  for 
oxygen  absorption,  without  which  it  could  not  live,  but  it  has 
also  remarkably  thickened  its  leaves  and  appressed  them 
vertically  against  the  stems  in  order  to  protect  itself  from  loss 
of  water,  for  reasons  which  have  been  already  stated. 

From  the  history  and  general  relation  of  this  mangroove 
to  the  Verbena  family,  we  judge  that  this  adaptation  is  of 
comparatively  recent  date.  When  removed  to  dry  cultivation 
it  loses  all  these  characteristics  in  the  first  offspring.  In  the 
case  of  the  Cypress  we  have  not  merely  theoretical  reasoning 
from  family  relationship,  but  also  definite  data  from  fossil 
remains,  which  prove  that  it  was  a  dry  land  form  in  a  very 
recent  geologic  age,  and  that  its  aquatic  habits  are  modern. 
It  is  certainly  curious,  and  you  may  interpret  it  as  you  please, 
that  both  these  plants,  when  subjected  to  opposite  conditions, 
immediately  lose  their  acquired  characters.  In  the  Australian 
plants,  on  the  contrary,  similarly  acquired  characteristics  under 
opposite  conditions  are  perfectly  permanent.  That  they  have 
been  in  this  condition  for  an  immensely  longer  period  of  time, 
and  that  in  consequence  this  development  is  so  stamped  upon 
their  parent  stock  that  it  reappears  generation  after  generation, 
even  when  withdrawn  from  their  causal  surroundings,  is, 
perhaps,  the  key  to  this  riddle. 

Let  me,  then,  remind  you  once  more  of  the  almost  infinite 
variety  and  diversity  of  plant  forms,  and  that,  as  seen  in 
nature,  we  can  generally  trace  the  relationship  between  the 
peculiarities  of  the  plant  and  its  surroundings  ;  also,  that  in 
general,  these  peculiarities,  no  matter  what  they  may  be, 
reproduce  themselves  in  the  offspring.  Let  me  state  once 
more  that  any  plant  which  we  may  select  as  an  example,  no 
matter  how  peculiar  in  form  or  habit  of  growth,  gives  us  an 
expression  in  this  peculiar  form  and  special  habit  of  the  forces 
which  have  surrounded  it  and  touched  it  all  the  way  down  its 
long  line  of  descent,  from  its  earliest  more  simple  and  primary 
condition  to  its  present  more  complete  expression  of  plant  life. 


NINTH    LECTURE. 


IRRITO-CONTRACTILITY    IN    PLANTS. 

Prof.    J.    IVIUIRHEAD    MACFARLANE,    D.    Sc. 

In  a  paper  published  by  me  about  nine  months  ago,  I 
showed  that  the  generally  accepted  view  that  the  leaf  of 
Dioiicea  contracted  after  one  stimulus  of  the  irritable  hairs  was 
incorrect,  and  that  two  stimuli  were  necessary  to  cause  contrac- 
tion. The  other  phenomena  connected  with  leaf-closure,  and 
described  in  the  paper,  were  so  remarkable  as  to  cause  me  to 
inquire  whether  these  phenomena  were  unique  in  the  vegetable 
kingdom,  or  whether  conditions  could  be  traced  that  connected 
Dioncea  with  other  sensitive  plants. 

The  behavior  of  the  leaf  of  Dioncea  to  mechanical  stimuli 
given  at  varying  intervals  of  time  was  such  as  to  suggest  a 
very  definite  and  exact  contraction  of  the  protoplasm  of  certain 
cells.  The  outcome  of  the  inquiries  which  are  epitomized  in 
the  present  lecture,  and  which  I  hope  in  time  to  bring  forward 
in  extended  form,  proves  that  in  the  vegetable  as  in  the 
animal  kingdom,  we  have  to  do  with  a  true  contractile 
tissue.  Further,  among  those  higher  plants  that  we  are  now 
to  study,  this  tissue  is  made  up  of  cells,  each  consisting  of  an 
irrito-contractile  protoplasmic  sac  enclosing  a  quantity  of  sap, 
and  each  cell  is  joined  to  neighboring  cells  by  protoplasmic 
processes  that  pass  through  minute  pores  in  the  common 
cellulose  membranes. 

In  order  to  make  clear  the  relation  that  is  shown  by  many 
sensitive  leaves  to  environmental  stimuli,  it  may  not  be  inap- 
propriate to  indicate  first  the  possible  movements  that  such 
leaves  can  perform,  as  generally  stated  in  memoirs  and  text- 
books on  the  subject.     A  plant  of  the  common  yellow  sorrel 


1 86  BIOLOGICAL   LECTURES. 

{Oxalis  strictd)^  if  examined  on  a  quiet  and  moderately  cool 
day  when  the  temperature  is  25°  C,  will  show  the  trifoliate  leaf 
fully  expanded,  and  the  three  leaflets  so  placed  on  their  stalks 
that  their  surfaces  lie  at  right  angles  to  the  sun's  rays  ;  i.e ., 
they  are  not  only  heliotropic  in  that  they  grow  toward  the 
light,  but  they  are  diaheliotropic  in  that  they  can,  if  need  be, 
so  place  their  surfaces  to  the  light  as  to  receive  the  rays 
at  right  angles.  But  if  the  temperature  rise  to  29°-  30° 
C.  in  the  shade,  the  leaflets  will  begin  to  fall  down  ;  and  if 
a  steady  increase  in  temperature  goes  on,  they  will  continue 
to  fall  till  at  33°  C.  they  will  incline  downwards  back  to  back. 
This  day-movement  has  long  been  known  to  occur  in  many 
plants,  and  was  regarded  as  a  means  by  which  the  leaves 
were  screened  from  intense  illumination  ;  but  my  colleague. 
Prof.  W.  P.  Wilson,  considers  it  to  be  a  heat-movement,  or  an 
attempt  on  the  part  of  the  plant  to  screen  itself  from 
intense  solar  thermal  action.  As  connected  with  the  varying 
results  of  stimulation  on  different  species  afterward  to  be 
described,  it  may  here  be  noted  that  Oxalis  stricta  shows 
distinct  heat-movement  at  29°  C. ;  Oxalis  Deppei  at  31°  C; 
Oxalis  dendroides  at  33°-34°  C.  ;  while  the  common  sensitive 
plant  {Mimosa  pudica)  that  has  thin  and  apparently  delicate 
leaflets  only  becomes  affected  when  the  shade  temperature 
rises  to  37°  C.  This  movement,  described  by  Darwin  as  a 
paraheliotropic  one,  I  propose  to  term  'parathermotropic' 

But  as  the  sun's  rays  become  tempered  in  the  afternoon,  or 
as  plants  formerly  exposed  to  the  full  heat  of  the  rays  get 
sheltered  by  foliage,  the  flat,  expanded  condition  is  resumed. 
Toward  the  approach  of  evening  the  leaflets  again  begin  to 
fall,  and  by  8.15  or  8.30  during  midsummer  have  taken  up  the 
same  position  that  they  had  during  the  heat  of  the  day.  This 
night-sleep,  or  nyctitropism,  has,  with  every  show  of  reason, 
been  viewed  by  Darwin  and  others  as  a  protection  against  too 
rapid  radiation  of  heat  and  reduction  of  temperature  in  the 
tissues.  We  would  emphasize  it,  then,  that  alike  during  the 
parathermotropic  and  nyctitropic  states  the  leaflets  of  Oxalis 
stricta  are  similarly  placed.  The  nyctitropic  position  is 
retained   till   the  following   morning,  and   in   some  plants,   at 


IRRITO-CONTRACTILITY  IN  PLANTS.  187 

least,  we  have  evidence  for  believing  that  the  effects  of  it  are 
not  fully  overcome  till  7  or  7.30  a.m.,  in  June  or  July. 

The  movements  now  described  are  characteristic  of  a  large 
series  of  plants  belonging  to  many  natural  orders,  but  the 
group  Oxalidcce  of  the  order  Geraniacece,  and  the  order 
LeguminoscB  probably  include  between  them  about  three- 
fourths  of  the  entire  number. 

You  are  doubtless  all  aware,  however,  that  leaves  or  leaf- 
parts  may  exhibit  movements  which  serve  a  different  purpose 
in  the  economy  of  the  plants  that  bear  them.  The  leaves  of 
Dioncea  and  Drosera,  as  well  as  tendriliform  leaves  and  leaflets, 
are  examples  in  point ;  and  the  question  naturally  presents  itself, 
—  How  are  these  movements  effected  }  Before  attempting  an 
answer,  we  propose  to  lay  before  you  the  results  of  observa- 
tions and  experiments  which  may  aid  in  the  solution  of 
the  question. 

Naturally,  in  the  vegetable  as  in  the  animal  world,  irrito- 
contractility  can  only  be  started  by  stimuli  of  a  mechanical, 
chemical,  thermal,  luminous,  or  electrical  nature.  For  several 
reasons,  I  can  only  treat  briefly  here  the  effect  of  thq  first  three 
forms  of  energy,  and  I  will  select  plants  for  illustration  in  the 
order  that  seems  most  suited  for  elucidating  the  subject. 
First,  we  may  recapitulate  regarding  Dioncea.  As  my  published 
researches  show,^  a  summation  of  two  mechanical  stimuli  is 
ordinarily  necessary  to  start  contraction.  Further,  these  must 
be  applied  with  a  time  interval  between  of  at  least  \  second  ; 
for  if  two  stimuli  are  given  in  rapid  succession,  both  are  propa- 
gated through  the  protoplasm  as  one  wave,  so  far,  at  least,  as 
motion  of  contraction  is  the  visible  outcome.  But  though  one 
stimulus  or  two  rapidly  applied  stimuli  are  insufficient  to  start 
contraction  of  the  leaf-halves,  we  know  that  active  molecular 
changes  are  in  process,  for  the  leaf-halves  exhibit  delicate  but 
visible  wave  impulses  passing  along  them  from  base  to  apex, 
while  Burdon  Sanderson  has  demonstrated  that  active  elec- 
trical changes  are  going  on.  After  a  second  mechanical 
stimulus,  or  three,  if  two  are  rapidly  applied,  the  leaf  closes 
partially,  —  i.  ^.,   the  marginal    bristles   loosely   interlock.      If 

1  Bot.  Cont.  Univ.  Penn.,  Vol.  I,   No.  i,  1892. 


1 88  BIOLOGICAL   LECTURES. 

the  leaf  be  not  further  irritated  by  some  instrument,  or  by  a 
caught  animal,  it  slowly  relaxes  after  12-15  hours;  but  if 
additional  stimuli  are  given,  the  leaf  gradually  and  firmly 
tightens  up  till  its  margins  become  recurved.  Prolonged 
stimuli,  either  of  a  mechanical,  chemical,  or  electrical  nature, 
start  eventually  (after  8-10  hours  usually)  the  flow  of  an  acid 
secretion  from  glands  that  cover  both  halves  of  the  leaf.  It  is 
clear,  therefore,  that  complete  contraction  of  DioncBa  leaf  can 
only  be  effected  by  a  summation  of  stimuli  ;  and  such  stimuli 
may  either  be  partially  or  entirely  mechanical,  chemical,  or 
electrical.  I  have  further  shown,  contrary  to  prevailing 
opinions,  that  not  merely  the  three  hairs  of  each  leaf -half,  but 
the  entire  surface  is  irrito-contractile.  Thus,  a  minute  bit  of 
ice  or  a  drop  of  hot  water  placed  on  any  part  of  the  leaf  away 
from  the  hairs,  also  a  forceps'  pinch,  a  mechanical  shock,  and 
many  chemical  agents,  excite  to  closure. 

We  have  already  said  that  the  time-interval  between  two 
shocks  may  be  too  short  to  start  contraction,  but  it  is  equally 
true  that  too  great  a  time  interval  is  attended  with  no  visible 
change  ;  in  other  words,  the  piling  on  of  the  second  stimulus 
to  the  first,  if  too  long  delayed,  is  insufficient  to  effect  closure. 
With  an  interval  between  of  50-60  seconds,  at  a  temperature 
of  I4°-2I°  C,  contraction  takes  place  after  a  second  excitation; 
and  I  stated  that  if  the  interval  were  increased  to  90-120 
seconds,  the  strength  of  the  two  was  almost  entirely  cancelled. 
Through  the  kindness,  however,  of  my  friend  Mr.  Aldrich 
Pennock,  I  have  studied  plants  in  his  hot-houses  at  high  tem- 
peratures (35^-40°  C),  and  find  that  the  effects  of  previous 
stimuli  can  be  retained  for  4  minutes  at  least.  But  a 
second  stimulus  applied  4  minutes  after  the  first  causes  no 
visible  movement  of  closure  ;  a  third,  4  minutes  after  the 
second  is  similar ;  and  not  till  the  sixth  stimulus  does  an 
almost  inappreciable  contraction  of  the  halves  take  place. 
Summation  of  successive  stimuli  from  the  eighth  to  the 
twelfth  gives  added  force  —  sufficient  to  bring  the  halves 
together.  Here,  then,  is  an  irritable  tissue  that  steadily 
contracts,  or  prepares  for  contraction,  through  a  period  of 
from   30-45   minutes. 


IRRITO-CONTRACTILITY  IN  PLANTS.  1 89 

The  conditions  thus  revealed  by  Dioncea  were  so  arresting 
as  to  cause  me  to  inquire  whether  similar  phenomena  might 
not  be  demonstrated  in  other  sensitive  plants.  Botanists 
have  long  been  acquainted  with  certain  species  which  from 
their  contractile  movements  were  aptly  designated  ''  sensitive 
plants."  These  included  species  of  Oxalis,  Averrhoa,  Mimosa^ 
Cassia,  ScJirarikia,  etc.,  some  of  which  were  considered  to  be 
highly  irritable,  others  less  so,  and  others,  again,  scarcely 
deserving  the  name.  The  best  account  hitherto  given  of  the 
action  of  some  of  these  when  affected  by  mechanical  stimuli 
is  to  be  found  in  Pfeffer's  PJianzeiiphysiologic  (pp.  224-254), 
where  Mimosa  pudica  and  Oxalis  acetosclla  are  chiefly  dealt 
with. 

Now  I  hope  not  only  to  show  you  that  various  transition 
types  exist  between  such  roughly  classified  groups  as  are 
expressed  in  the  descriptions  "very  sensitive,"  "slightly  sensi- 
tive," "  scarcely  sensitive,"  but  that  under  given  environmental 
conditions  all  exhibit  a  definite  irrito-contractility,  characterized 
by  varying  degrees  of  latent  period,  of  contraction  period,  of 
expansion  period,  and  of  summation  effects,  or,  to  put  it  in  a 
broader  sense,  that  tJie  same  pJienomcna  of  irrito-contractility 
are  encountered  in  the  vegetable  as  in  the  animal  kingdo^n. 
The  optimum  temperature  for  most  of  the  plants  now  to  be 
mentioned  is  an  average  of  26°  C,  exposure  for  a  short  time  or 
for  a  prolonged  period  to  low  temperatures  (8°-i5°  C)  causing 
an  extension  of  the  latent  period,  slower  rate  of  contraction, 
and  a  reduced  power  of  conducting  stimuli. 

As  being  both  a  common  plant  and  a  central  type  in  its 
physiological  behavior,  we  may  now  take  the  field  and  wayside 
weed  Oxalis  stricta,  the  yellow  sorrel.  When  plants  are  grown 
in  a  rather  shady  situation  and  exposed  to  a  temperature  of 
i8°-24°  C,  the  leaves  have  a  rich  green  color,  and  the  three 
leaflets  together  form  a  triradiate  rosette.  We  need  not  now 
refer  to  structural  details  further  than  to  say  that  at  the  base 
of  each  leaflet  is  a  little  cushion  composed  chiefly  of  small, 
densely  aggregated,  and  vacuolated  cells  forming  a  typical 
sensitive  pulvinus.  After  a  sharp  but  delicate  mechanical 
stimulus  applied  with  a  pencil  or  other  instrument  to  a  terminal 


I90  BIOLOGICAL   LECTURES. 

leaflet,  a  latent  period  oi  i\  seconds  elapses,  followed  by  a 
period  of  slow  but  gradually  accelerating  contraction  during 
the  next  4  seconds.  From  the  seventh  to  the  twentieth 
second  the  motion  is  rapid,  but  thereafter  slows  down  gradually 
to  the  thirtieth  second,  and  then  becomes  increasingly  slow  till 
the  forty-fifth  second  when  the  contraction  ceases.  After 
15-18  minutes  expansion  begins,  and  a  very  slow  rise  can  be 
traced  till  the  leaf  regains  its  expanded  state  in  45-50  minutes. 
The  angle  through  which  such  a  leaf  falls  is  on  the  average 
37°,  but  varies  with  the  daily  periodicity  of  cell  tension,  as  well 
as  the  temperature  and  moisture  of  the  air  and  soil. 

It  should  be  stated  that  young,  active  —  not  necessarily 
growing  —  leaves  are  to  be  preferred  for  experiment,  but  even 
the  oldest  and  fully  matured  leaves  are  sensitive  to  a  definite 
degree,  though  less  so  than  those  younger.  Some  interesting 
statistics  will  be  adduced  later  in  this  connection. 

When  the  three  leaflets  of  a  leaf  are  simultaneously  excited, 
all  contract,  and  the  movement  shown  is  as  follows:  The 
terminal  leaflet  simply  drops  and  folds  its  halves  together 
more  or  less  toward  their  upper  faces,  but  the  two  side  leaflets 
move  forward  and  downward  so  that  each  describes  a  segment  of 
an  ellipse.  If  care  be  taken,  however,  to  stimulate  the  terminal 
one  of  the  three,  it  alone  will  contract,  or,  at  most,  the  side 
leaflets  will  move  to  a  small  extent.  This,  among  other  things, 
proves  that  the  capability  of  conducting  a  stimulus  through  its 
tissues  is  comparatively  feeble  in  this  species. 

In  no  case  have  I  found  that  a  single  shock  is  sufficient  to 
produce  a  contraction  approaching  in  amount  to  the  nyctitropic 
or  the  most  pronounced  parathermotropic  states.  The  angle 
fallen  through  varies  from  25°  to  48°.  A  summation  of 
stimuli,  however,  produces  very  different  results.  If  an  excited 
leaflet  be  left  till  the  downward  movement  has  ceased,  and 
a  second  stimulus  be  applied,  it  will  fall  still  further,  but 
through  a  less  angle  than  before,  and  its  motion  will  cease 
sooner  ;  if  a  third  stimulus  be  then  applied  there  will  be  an 
additional  fall  less  in  extent  than  the  second,  and  greatly 
less  than  the  first,  the  time  of  motion  being  correspondingly 
shortened.     A  fourth  stimulus  will  give  a  slight  but  appreciable 


IRRITO-CONTRACTILITY  IN  PLANTS.  191 

additional  contraction.  I  may  best  illustrate  by  a  concrete 
example  selected  at  random  from  many  others.  A  leaflet 
stimulated  fell  through  42°  in  45  seconds,  a  second  stimulus 
increased  the  angle  to  69°  within  38  seconds  after  rest,  a  third 
stimulus  increased  it  to  81°  after  33  seconds,  and  a  fourth  to 
84°  after  27  seconds. 

Thus,  by  four  successive  stimuli  applied  during  a  period  of 
143  seconds,  the  leaf  described  an  angular  movement  of  84°. 
But,  as  I  have  already  stated,  the  period  of  maximal  movement 
after  first  excitation  occurs  between  the  seventh  and  twentieth 
seconds.  Taking  advantage  of  this  fact,  by  shortening  the  time 
interval  between  the  stimuli,  the  same  amount  of  contraction 
can  be  got  in  a  much  shorter  time.  A  leaf  was  irritated  and 
allowed  to  contract  for  22  seconds,  when  it  had  fallen  through 
38°  ;  it  was  again  irritated,  and  allowed  to  contract  for  20 
seconds  when  it  had  fallen  through  61°.  Again  irritated  it 
fell  through  an  additional  15°,  and  after  the  fourth  stimulus 
had  fallen  through  81°. 

The  above  time-intervals  remain  wonderfully  constant  in  all 
active  leaves  when  the  environmental  conditions  remain 
constant,  but  a  distinct  shortening  of  the  latent  period  by  | 
to  \  second  was  noted  on  a  moist,  close  and  warm  morning  in 
early  July  after  a  thunder-storm  of  the  previous  evening.  It 
should  also  be  stated  that  when  the  plants  are  continuously 
exposed  to  such  high  shade  temperatures  as  35^-40°  C,  they 
become  smaller  in  size  and  irregular  in  action. 

We  now  turn  to  thermal  stimuli,  and  I  may  at  once  state 
that  ice  particles  produce  a  very  marked  effect  on  this  and  all 
other  sensitive  plants.  When  a  piece  weighing  \-\  grain  is 
placed  at  the  junction  of  three  leaflets  a  longer  latent  period 
than  for  mechanical  stimuli  ensues,  but  when  once  started 
contraction  steadily  proceeds  till  the  ice  has  melted  and  the 
resulting  water  has  attained  a  temperature  that  fails  to  excite 
the  protoplasm.  If  by  aid  of  a  pipette  or  blotting  paper  the 
water  is  sipped  off  and  a  fresh  bit  of  ice  is  placed,  contraction 
will  go  on  till  the  nyctitropic  position  has  been  reached.  But 
as  in  the  case  of  mechanical  stimuli  more  localized  action  can 
be  started,  for  if  ice  be  placed  not  on  the  pulvini   but  near 


192  BIOLOGICAL   LECTURES. 

the  base  of  the  terminal  leaflet,  the  latter  will  move  through 
a  large  angle,  while  the  side  leaflets  will  not  at  all  or  only 
slightly  participate.  A  bit  laid  similarly  on  one  of  the  side 
leaflets  will  make  it  move  independently  of  the  others.  By 
conducting  control  experiments  with  weights  equal  to  the 
particles  of  ice  used,  it  can  be  proved  that  cold  stimulus  and 
not  weight  of  the  particles  is  the  determining  factor. 

As  with  Dioncea,  so  here  a  drop  of  hot  water  and  the  appli- 
cation of  a  heated  wire  excite  to  contraction,  but  instead 
of  touching  analytically  on  these  I  should  prefer  to  dwell 
on  the  question  of  parathermotropism.  All  my  observations 
go  to,  show  that  this  is  largely  due  to  heat  stimulation 
of  the  irrito-contractile  cells,  acting  steadily  for  some  minutes 
on  these,  and  that  the  movements  can  be  hastened  or  arrested 
by  a  rise  or  fall  of  a  few  degrees  of  temperature.  Moreover, 
it  seems  undoubted  that  the  soil  temperature  has  much  to  do 
with  the  amount  of  contraction  that  each  leaf  undergoes.  It 
is  not  difficult  to  understand  why  this  should  be.  Given  a  soil 
on  which  Oxalis  is  growing  that  is  covered  by  a  pretty  close 
herbage,  above  which  the  plant  rears  its  tuft  of  leaves  ;  the 
soil  protected  from  the  sun's  rays,  and  retaining  its  moisture 
by  reason  of  the  roots  that  spread  through  it,  will  furnish 
currents  of  cool  water  that  will  constantly  rise  into  the  leaves 
of  the  plant.  Evaporation  of  the  surplus  moisture  thus  passed 
into  the  leaves  will  further  lessen  the  temperature  of  the 
tissues.  I  may  be  allowed  to  quote  only  one  set  of  statistics 
in  support.  On  a  close,  dull,  but  rather  warm  day,  with 
the  temperature  at  25°  C.  in  the  shade,  several  plants  were 
studied  that  grew  under  the  shade  of  trees,  and  amid  an 
abundant  herbage.  The  ground  temperature  was  23°  C.  All 
the  leaflets  were  either  fully  expanded  or  inclined  slightly 
upwards  from  their  point  of  union.  Another  set  grew  on  a 
rather  moist  bank  and  were  slightly  overshadowed  by  a  tree. 
The  thermometer  placed  alongside  the  plants,  and  like  them 
exposed  to  a  slightly  higher  than  the  true  shade  heat,  registered 
27°  C,  while  the  surface  of  the  soil  below  registered  25.5°  C. 
The  leaflets  were  flat  or  faintly  inclined  downwards.  Alongside 
a  third  set,  about  two  yards  from  the  last,  the  thermometer 


IRRirO-CONTRACTILITY  IN  PLANTS.  1 93 

registered  29.5°  C.  when  exposed,  and  27.5°  C.  on  the  ground. 
Some  plants  that  were  exposed  to  the  sun's  heat  grew  on  a 
rather  dry  soil  with  scant  herbage,  and  their  leaflets  were 
deflected  through  an  angle  of  52°  to  65°.  Lastly,  on  a  bit  of 
hard,  dry,  whitish  soil,  the  exposed  temperature  alongside  the 
plants  was  31°  C,  and  on  the  soil  33°  C.  The  leaflets  of 
the  plants  were  as  strongly  deflected  as  during  night-sleep. 

The  amount  of  moisture,  therefore,  that  is  drawn  from  a 
cool  shaded  soil  or  from  a  hot,  dry  soil  may  largely  determine, 
by  its  temperature,  the  stimulus  given  to  the  protoplasm  and 
the  position  that  the  leaflets  are  to  assume  accordingly.  A 
cooperating  factor  in  the  parathermotropic  movement  may  be 
a  lack  of  sufficient  moisture,  which,  in  all  sensitive  plants 
studied,  causes  flaccidity  and  a  want  of  tone  in  the  tissues. 

We  shall  have  occasion  in  treating  of  other  plants  to  speak 
of  the  action  of  such  chemicals  as  ammonia,  carbonate  of 
ammonia,  chloroform,  ether,  alcohol,  etc.,  which  all  act  as 
excitants. 

Oxalis  Deppei  is  a  large  succulent  species,  commonly  grown 
now  as  an  edging  plant  in  herbaceous  borders.  Each  leaf  is 
quadrifid,  and  examination  of  the  base  of  the  leaflets  reveals 
large  reddish  swellings  or  pulvini.  Mechanical  stimulus  is 
followed  by  a  latent  period  of  3I  seconds  ;  then  slow  but 
accelerating  contraction  is  observed  for  the  next  4  seconds, 
when  rapid  contraction  follows  for  22-23  seconds,  and  a  very 
gradual  slowing  down  goes  on  till  contraction  ceases  80-90 
seconds  after  stimulation.  The  striking  and  main  difference 
between  this  species  and  Oxalis  stricta  consists  in  the  con- 
traction period  being  about  twice  as  prolonged.  As  with 
Oxalis  stricta,  summation  series  can  be  obtained  that  vary 
with  the  time-intervals  between  stimuli  and  the  environmental 
surroundings. 

Observation  of  the  contraction  and  expansion  movements  of 
this  and  other  sensitive  plants  shows  that  each  is  made  up  of 
numerous  minor  contraction  and  expansion  waves  that  cause 
the  leaf  to  move  by  minute  jerks,  each  minor  contraction  phase 
during  the  great  period  of  contraction  being  much  greater  in 
amount  than   the   succeeding  expansion   phase.     In  all  prob- 


194  BIOLOGICAL   LECTURES. 

ability  this  is  due  to  the  gradual  passage  of  sap  through  the 
contractile  protoplasmic  layer  of  each  cell  and  the  elastic  recoil 
of  it  and  of  the  wall  as  additional  liquid  is  extruded  or  absorbed. 

I  now  pass  to  Oxalis  dendroides,  a  plant  eminently  suited  for 
investigations  like  the  present,  and  which  has  yielded  results 
as  interesting  as  they  were  unexpected.  For  a  supply  of  fine 
specimens  I  am  indebted  to  the  kindness  of  Mr.  G.  Oliver  of 
the  Washington  Botanic  Garden.  It  is  an  abundant  weed  in 
Brazil  and  is  often  confounded  with  Oxalis  sensitiva,  that  is 
native  from  Persia  to  China.  It  is  one  of  a  series  of  nearly 
related  forms,  some  of  which  like  the  present  have  a  simple 
unbranched  upright  habit,  while  others  incline  to  a  proliferous 
mode  of  growth.  Though  seldom  seen  outside  botanic  gardens, 
it  grows  with  the  utmost  readiness,  fruits  freely,  and  scatters  its 
seeds  widely.  Four  noteworthy  points  can  be  readily  demon- 
strated on  this  species,  though  witnessed  less  perfectly  in 
others.  These  are :  First,  that  the  latent  period  varies  accord- 
ing to  the  age  of  the  leaf;  second,  that  a  gradual  propagation 
of  stimulus  from  base  to  apex  or  vice  versa  can  be  shown  to 
exist;  third,  that  the  rate  of  propagation  of  the  contraction- 
stimulus  can  be  exactly  measured  ;  and  fourth,  that  the  rate  of 
contraction  and  expansion  of  leaflets  is  quickest  in  young  and 
slowest  in  old  leaves. 

If  the  tip  of  the  blade  of  a  terminal  leaflet  be  stimulated 
by  a  forceps  snip,  in  an  atmosphere  whose  temperature 
is  28° -32°  C,  it  and  the  companion  leaflet  will  fall 
down  through  an  angle  of  40°-45°  in  about  20  seconds. 
That  irritation  of  a  leaflet  should  excite  to  a  rapid  movement 
not  merely  of  one  but  of  neighboring  leaflets,  suggests  the  idea 
that  at  least  some  of  the  cells  of  every  leaflet  can  conduct  a 
stinmlns.  This  idea  is  entirely  confirmed  by  many  other 
experimental  results.  If  the  leaflet  that  has  been  irritated  be 
part  of  an  old  leaf,  the  succeeding  pairs  of  leaflets  will  close  in 
regular  succession  from  apex  to  base  with  a  time  interval 
between  each  pair  of  2\  seconds.  By  this  we  mean  the  time 
required  for  propagation  of  the  shock  from  one  pair  of  pulvini 
to  another  pair  below,  and  succeeding  contraction  of  the  living 
protoplasm  of  the  different  cells  in  the  path  of  the  stimulus. 


IRRITO-CONTRACTILITY  IN  PLANTS.  1 95 

But  as  I  shall  point  out  later,  it  would  be  a  mistake  to  suppose 
that  the  actual  rate  of  propagation  of  stimulus  from  apex  to 
base  of  the  leaf  is  so  slow  as  this.  If  the  leaf  operated  on  was 
the  fifteenth  from  the  growing  apex  of  the  stem  and  the  tenth 
leaf  be  now  chosen  and  similarly  operated  on,  the  time  interval 
between  contraction  of  succeeding  pairs  of  leaflets  will  be 
1 1 -2  seconds;  with  the  seventh  leaf  from  the  apex  the  interval 
will  be  i^-if  seconds;  and  finally  a  delicate  light-green  leaf, 
such  as  the  second  or  third  from  the  apex,  shows  closure  of 
successive  pairs  with  an  interval  between  of  i-i|-  seconds. 
The  latent  period  shown  after  general  stimulus  in  such  a  set 
of  leaves  is  equally  variable,  and  under  optimum  surroundings 
is  only  |-|  of  a  second  in  young  leaves  such  as  the  third  from 
the  apex,  |-i  second  in  the  seventh  or  eighth,  i-ij  in  the 
tenth  or  eleventh,  and  i  j-i|  in  the  fifteenth. 

As  mentioned  above,  the  angle  through  which  the  leaflets 
fall  on  excitation,  is  from  40° -45°.  If  a  general  shock 
be  given  to  the  entire  leaf,  the  leaflets  fall  simultaneously 
through  an  angle  of  equal  amplitude.  But  summation  action 
can  now  be  brought  to  bear,  for  on  second  stimulus  the  leaflets 
will  fall  through  an  angle  of  24°-28°  and  in  a  correspondingly 
short  time.  On  third  stimulus  the  leaflets  will  fall  through 
I2°-I4°  in  a  still  shorter  interval,  while  a  fourth  stimulus  will 
cause  a  fall  through  4°-  5°  in  a  shorter  interval  than  the  last. 
By  this  time  the  leaflets  will  be  folded  downward  back  to  back 
as  in  night-sleep,  or  a  fifth  stimulus  effecting  a  slight  additional 
movement  may  be  needed  to  complete  the  process. 

A  small  bit  of  ice  weighing  ^  of  a  grain,  if  delicately  placed 
on  the  tip  of  a  terminal  leaflet  so  as  not  to  touch  or  directly 
stimulate  the  pulvinus  cells,  starts  motion  in  the  one  opposite 
within  7  seconds.  A  steady  impulse  is  then  propagated  down 
the  leaf- stalk  from  pair  to  pair,  the  time  interval,  as  in 
mechanically  stimulated  leaves,  depending  on  the  age  of  the 
leaf.  If,  as  has  repeatedly  been  noticed,  a  pair  of  leaflets  is 
encountered  which  is  somewhat  benumbed  from  the  effect  of 
previously  applied  chemical  or  other  agents,  these  will  remain 
motionless,  or  nearly  so,  but  the  same  interval  of  time  will  elapse 
before  the  next  pair  beneath  will  contract  as  would  have  been 


196  BIOLOGICAL   LECTURES. 

needed  to  start  movement  in  the  benumbed  ones  as  well  as  in 
these.  On  several  occasions,  a  behavior  has  been  noted,  both  in 
Oxalis  deiidroides  and  the  common  sensitive  plant,  that  is  worth 
recording,  whether  the  suggested  explanation  of  the  behavior 
is  the  correct  one  or  not.  A  bit  of  ice  laid  directly  on  the 
pulvini  of  two  opposite  leaflets  failed  to  excite  them  to  motion 
and  even  a  pair  beneath  would  only  partially  contract,  while 
those  still  further  down  would  move  in  normal  fashion.  I 
satisfied  myself  that  the  position  and  weight  of  the  ice  particle 
offered  no  obstacle,  and  learned  also  that  if  within  20-30 
seconds  the  ice  be  removed,  the  leaflets  after  an  added  interval 
of  7-15  seconds  fall  backwards  as  if  recently  stimulated.  We 
believe  a  probable  explanation  here  to  be  that  during  the  latent 
period  of  excitation,  the  ice  had  so  lowered  the  temperature  of 
the  subjacent  cells  as  to  benumb  the  protoplasm,  which  only 
regained  its  contractile  properties  with  returning  irritability 
after  removal  of  the  ice. 

We  may  next  inquire  whether  a  peripheral  or  centripetal 
stimulus  is  propagated  to  the  leaf  base  or  to  the  stem  more 
rapidly  than  a  centrifugal  stimulus  initiated  at  the  basal  leaflets. 
The  only  plant  that  has  hitherto  been  experimented  on  is 
the  common  sensitive  plant,  but  Dutrochet  and  Bert  expressed 
different  views.  Oxalis  is  much  more  convenient  for  the  deter- 
mination of  this  question.  Each  leaf  carries  15-24  pairs  of 
leaflets.  A  particle  of  ice  placed  on  the  pulvini  of  the 
middle  pair,  i.e.,  the  tenth  if  there  are  19  pairs,  will  excite  all 
the  pairs  above  it  within  15-17  seconds,  but  21-23  seconds  will 
elapse  before  the  lowest  pair  in  such  a  leaf  as  the  tenth  from 
the  apex-bud  closes.  With  the  ice  in  varying  positions  and 
on  leaves  of  different  age  I  have  invariably  found  that  a  cen- 
trifugal is  more  rapid  than  a  centripetal  impulse,  and  I  have 
studied  many  examples.  But  the  records  are  less  satisfactory 
as  regards  simultaneous  basal  and  apical  initiation  of  excitation, 
though  the  balance  of  experimental  proof  is  in  favor  of  centri- 
fugal stimulus. 

As  with  sensitive  plants  in  general,  carbonate  of  ammonia  is 
a  powerful  stimulant,  and  its  rapidity  is  proportioned  to  the 
strength    of    the    solution.     When    a    small   drop  of    a   20  ^ 


IRRITO-CONTRACTILITY  IN  PLANTS.  I  97 

solution  is  laid  on  the  tip  of  a  terminal  leaflet,  striking  changes 
occur.  Both  of  the  terminal  leaflets  close  within  7  seconds,  and 
the  succeeding  pairs  below  begin  to  close  at  the  rate  already 
given.  But  before  5  or  6  pairs  out  of,  it  may  be,  19-22  have 
closed,  a  leaflet  near  the  base  may  be  noticed  to  twitch,  or,  as 
often  happens,  leaflets  on  distinct  leaves,  that  are  placed 
however,  on  the  same  side  of  the  plant  as  the  excited  one,  may 
twitch  or  even  fold  together  in  succession,  or  move  irregularly. 
When  this  was  first  observed,  it  seemed  likely  that  the  volatile 
fumes  were  the  cause,  but  though  they  do  act  as  slow  excitants, 
I  was  soon  convinced  that  twitches  and  other  movements  give 
us  a  hint  as  to  the  true  rate  of  propagation  of  stimuli  through 
the  special  conducting  tissue,  and  that  the  rate  of  conduc- 
tivity is  greatly  more  rapid  than  that  more  specialized  or 
detailed  exhibition  of  it  which  ends  in  the  falling  back  of  the 
leaflets. 

Before  passing  from  this  species  I  may  observe  that  the 
leaves  as  a  whole  seem  to  be  very  feebly  responsive  to  shocks, 
but  they,  as  well  as  the  flower  stalks,  perform  periodic  move- 
ments of  great  regularity.  There  seems  to  be  an  equally 
marked  periodic  movement  in  the  carpels  at  time  of  dehiscence, 
for  they  always  open  in  the  morning  while  still  green,  and 
after  scattering  of  the  seeds  in  the  forenoon  they  close  again 
permanently. 

The  above  species,  I  believe,  will  prove  to  be  the  most 
valuable  plant  that  can  be  chosen  for  laboratory  purposes,  not 
alone  to  the  botanist,  but  as  well  to  the  animal  physiologist. 

Mimosa  piidica  deserves  well  its  common  appellation,  '' tJie 
se7isitive  plant,''  for  whether  we  take  account  of  its  short  latent 
period,  rapid  contraction,  relatively  rapid  expansion,  delicacy  of 
sensitiveness  and  rapidity  of  propagation  of  an  impulse,  it 
deservedly  earns  its  popular  name.  It  has  engaged  the 
attention  of  such  earnest  workers  as  Lindsay,  Dutrochet, 
Briicke,  Sachs,  Batalin,  Bert,  Millardet,  Pfeffer,  and  during 
the  past  year  or  two  of  Cunningham  and  Gaston  Bonnier. 
But  much  yet  remains  to  be  done. 

While  tracing  out  and  comparing  the  contraction  and  expan- 
sion periods  in  plants  six  weeks  old,  ten  weeks  old,  and  fifteen 


198  BIOLOGICAL  LECTURES. 

weeks  old  respectively,  it  was  found  that  expansion  in  a  leaf  of 
one  of  the  first  took  place  within  4^-5^  minutes,  in  one  of  the 
second  (selecting  the  fifth  or  sixth  leaf  from  the  cotyledons) 
the  expansion  period  was  8^-10^  minutes,  in  one  of  the  third 
(selecting  the  eleventh  or  twelfth  leaf)  the  expansion  period  was 
13-16  minutes.  To  fully  verify  the  observations,  I  compared 
plants  of  known  age  in  several  establishments,  and  found  the 
results  in  all  cases  to  agree,  the  longest  period  occupied  in 
expansion  —  23  minutes  —  having  been  witnessed  in  a  plant 
kindly  placed  at  my  disposal  by  Dr.  Schively  and  which  was 
four  or  five  years  old,  but  had  formed  fresh  shoots  for  the 
season. 

The  relative  rapidity  of  contraction  and  expansion  shown  by 
leaves  at  different  levels  on  the  stem  is  to  a  large  extent  retained 
during  the  life  of  each,  though  with  age  the  movements 
become  more  sluggish. 

As  regards  rate  of  propagation  of  stimuli  Dutrochet  calculated 
it  to  be  2-3  m.  m.  per  second  in  the  stem,  and  8-15  m.  m.  in 
the  petiole.  Bert  in  comparing  his  own  results  with  those  of 
Dutrochet  considered  that  this  estimate  was  much  too  high  and 
gave  2-5  m.  m.  per  second  as  the  rate.  But  undoubtedly  the 
estimates  of  both  observers  are  greatly  below  the  true  rate  for 
certain  parts  of  the  leaf,  as  the  following  will  prove.  With 
forceps  I  delicately  pinched  the  tip  of  a  terminal  leaflet  borne 
on  a  primary  leaflet  that  had  17  pairs  of  secondary  ones.  The 
end  leaflets  closed  within  a  second,  the  next  lower  pair  after  5 
seconds,  and  all  had  closed  within  9^  seconds.  Now,  even  if  we 
grant  that  the  wave  of  excitation  started  immediately  on  applica- 
tion of  the  excitatory  stimulus,  the  entire  distance  having  been 
65  m.  m.  an  average  rate  of  7  m.  m.  per  second  would  be  the 
outcome.  But  many  experiments  which  cannot  here  be  detailed 
convinced  me  not  only  that  excitations  can  be  started  over  any 
part  of  the  leaflets,  but  that  there  is  a  rapid  propagation  along 
the  leaf  stalk.  The  starting  of  cold  stimuli  by  ice  clearly 
verified  this.  Whether  delicately  held  in  the  leaf  axil  against 
the  pulvinus,  or  placed  alongside  the  pulvinus  or  against  its 
lower  surface  that  is  specially  irritable,  a  bit  of  ice  made  the 
leaf   fall   within    i^  — if    seconds.       Now   the   length   of    each 


IRRITO-CONTRACTILITY  IN  PLANTS.  1 99 

primary  petiole  is  48-55  m.  m.  If  a  bit  of  ice  or  a  drop  or  two 
of  ice-water  be  applied  to  its  distal  end,  the  petiole  will  fall  in 
as  short  a  time  as  already  stated.  This  shows  that  in  the 
primary  petiole  at  least,  the  rate  of  propagation  is  not  less  than 
25  m.  m.  per  second,  a  rate  quite  equal  to  that  met  with  in  the 
contractile  tissues  of  various  animals. 

Confirmatory  evidence  is  got  by  the  use  of  various  chemicals. 
When  a  minute  drop  of  carbonate  of  ammonia  is  delicately 
placed  on  the  tip  of  a  young  leaflet,  one  notices  X\\2X  for  the  first 
4-4^  seconds  a  chajige  m  color  or  density  gradually  creeps  doivn 
the  leaf  substance,  but  by  the  time  that  this  has  spread  over  half 
the  leaflet  contraction  ensues,  and  thereafter  the  other  leaflets 
close  at  the  time  rate  already  given  for  them.  But  even  by  the 
time  that  the  second  or  third  pair  has  contracted,  twitching  and 
partial  closure  of  pairs  near  the  leaf  base  prove  that  the  stimu- 
lus has  already  travelled  down  the  secondary  mid-rib  greatly 
faster  than  is  indicated  by  the  movement  of  the  leaflets. 

Ether  is  a  very  serviceable  stimulant,  though  I  will  not  now 
enter  into  disputed  questions  as  to  the  action  of  its  vapor.  A 
small  drop  of  20/0  ether  was  placed  on  one  of  two  end 
leaflets.  The  others  closed  in  succession  within  8  seconds,  the 
leaf  fell  at  14  seconds,  within  18  seconds  the  leaf  next  above 
fell,  and  within  31  seconds  the  leaf  still  higher.  From  the 
leaflet  tip  to  the  pulvinus  of  the  last  mentioned  leaf,  the  distance 
was  160  m.  m.,  so  that  the  average  rate  of  propagation  necessary 
for  movement  of  parts  was,  at  least,  5  m.  m.  a  second.  Guided 
by  Elfving's  experiments  on  various  of  the  lower  plants,  where 
he  found  that  2  to  5  /o  chloroform  and  15  ^  ether  might  not 
prove  permanently  injurious  to  some  organisms,  experiments 
were  made  with  6  fo  ether.  When  a  drop  was  applied  to  the 
tip  of  a  leaflet  very  slight  movement  followed  in  most  instances; 
in  three  cases  there  was  a  half-closing  of  the  terminal  leaflets, 
and  in  one  only  did  they  close,  to  re-open  again  in  4J-  minutes. 
In  two  of  them  the  second  and  third  pairs  of  leaflets  were 
visibly  affected  and  slightly  moved  upward  and  forward.  No 
injurious  effect  followed  the  application. 

Hot  water  and  heated  wire  applied  to  any  part  of  the  petiole 
or  of  the  leaflets  stimulate  rapidly. 


200  BIOLOGICAL   LECTURES. 

Sachs,  Pfeffer  and  others  have  noticed  that  Mimosa  plants 
when  left  unwatered  for  a  few  days  lose  their  power  of  con- 
tractility. This  is  true  of  all  irritable  plants  that  I  have 
examined,  and  is  capable  of  ready  explanation. 

My  plan  till  now  has  been  to  lead  you  up  from  one  or 
two  well-known  plants  that  exhibit  a  rather  sluggish  irrito- 
contractility  to  the  true  sensitive  plant  that  is  unique  in  its 
physiology.  I  propose  now  to  pass  down  the  scale  again  and 
briefly  pass  in  review  some  common  field  weeds,  that  may,  like 
Oxalis  stricter,  be  found  around  us  here.  Had  time  permitted 
I  should  'have  pointed  out  how  the  sensitive  plant  is  related 
to  its  near  ally.  Mimosa  bipulina,  and  this  again  to  Mimosa 
sensitiva,  both  of  which  I  have  had  the  opportunity  of  studying 
from  the  Washington  Botanic  Garden,  through  the  kindness  of 
Mr.  Oliver.  But  from  the  last  an  easy  transition  is  established 
with  our  Eastern  American  weed.  Cassia  nictitans,  while  C. 
chamaecrista  unites  it  again  with  C.  marylaiidica,  that  shows 
a  very  feeble  though  measurable  response  to  mechanical, 
chemical,   and  other  stimuli. 

Cassia  nictitans,  the  wild  sensitive  plant,  is  generally  stated 
in  botanical  manuals  to  be  ''  somewhat  sensitive."  When  a 
delicate  mechanical  shock  is  given  to  the  leaf,  close  observation 
will  show  that  the  leaflets  almost  instantaneously  change 
position  slightly,  but  succeeding  to  this  is  what  I  can  only  at 
present,  for  want  of  better  knowledge,  designate  as  a  latent 
period  of  5^  seconds.  Thereafter  the  leaf  stalk  falls  through 
an  angle  of  15-23°  and  the  leaflets  simultaneously  move 
forward  and  rotate  inward  so  that  their  outer  edges  become 
uppermost  as  in  the  sensitive  plant.  This  is  accomplished  in 
85-86  seconds  on  the  average,  and  by  the  end  of  that  time  the 
leaflets  are  half-closed.  But  if  a  second  shock  be  given  after 
the  effects  of  the  first  have  ceased,  the  leaf  will  now  fall  through 
an  angle  of  8-9  °  and  the  leaflets  will  come  together  till  they 
nearly  lie  face  to  face  as  in  Mimosa  pudica.  A  third  stimulus 
may  even  give  slightly  added  results. 

An  interesting  feature  in  this  species  is  the  propagation  of 
stimuli  along  the  leaf  though  to  a  feebler  degree  than  in 
Mimosa.      As  many  of  you  must  have  observed,  a  brownish- 


JRIUTO-CONTRACTILITY  IN  PLANTS.  20I 

red  knob-like  gland  is  situated  on  the  upper  surface  of  the 
petiole,  about  3  m.  m.  below  the  insertion  of  the  lowest 
leaflets.  If  a  minute  drop  of  carbonate  of  ammonia  be 
cautiously  placed  on  it,  contraction  of  all  the  leaflets  ensues, 
proof  this  that  a  continuity  of  irritable  tissue  exists  between 
it  and  the  leaflets  that  are  inserted  above.  The  structural 
relations  of  this  gland  with  the  pulvini  of  the  leaflets  is  inter- 
esting, but  cannot  be  dealt  with  now.  Ice  and  cold  water, 
hot  water  and  dry  heat  stimuli  are  all  irritants  to  it,  as  are 
chloroform  and  ether  of  1 5  ^  strength  and  upwards.  These 
can  all  act  so  continuously  that  they  cause  the  leaf  to  fall 
and  the  leaflets  to  rise  to  the  extent  that  is  seen  in  the 
nyctitropic  state. 

The  hog  pea-nut  {AmphicarpcBa  monoica),  as  delicate  and 
graceful  as  it  is  abundant,  is  convenient  for  study  alike  in  the 
field  and  laboratory,  but  we  can  expeditiously  treat  it  along 
with  its  companions  of  our  woods  and  thickets,  the  tick  trefoils 
or  Desmodiums.  My  attention  has  been  mainly  confined  to 
three  species  of  the  genus,  viz.,  Dcsmodium  cajiescens,  Desmo- 
dm7n  paiiiciilatnni,  and  Dcsviodinm  rotinidifolijnn.  They  show 
a  degree  of  sensitivity  in  the  order  that  I  have  given  them. 
The  latent  period  in  A^nphicarpcea  and  Dcsuiodium  canesccns 
under  ordinary  conditions  is  3^^-34  seconds,  but  when  plants 
are  grown  in  a  green-house  it  is  shortened  to  2|-2|  seconds. 
In  Desmodiiim  paniculatinn  the  motion  is  so  slow  that  I  have 
failed  as  yet  to  determine  it  exactly. 

The  period  of  contraction  is  considerably  longer  than  in  any 
yet  described  and  is  for  AmpJiicarpcsa  i  50-  160  seconds  on  clear 
dry  days,  and  180-200  on  close  moist  days;  for  Dcsinodiuni 
canesce7is  and  Desmoditnh  pajticulaiitm  from  120-140  seconds. 
The  amplitude  of  movement  in  Arnphicarpcea  is  greater,  however, 
for  equal  stimuli  than  in  the  two  last,  thus  while  Amphicaipcea 
after  one  stimulus  falls  in  the  forenoon  of  a  dry  day  through  as 
much  as  65-70°,  the  others  seldom  fall  through  more  than 
48-50°.  But  a  result  got  with  some  plants  of  Ajuphicarpcea 
on  a  close,  warm,  but  dull  day,  is  worth  recording.  Like  most 
leguminous  species  it  raises  its  leaflets  during  the  parathermo- 
tropic  period  so  as  to  point  the  tips  at  the  sun.     At    12.30  a 


202  BIOLOGICAL   LECTURES. 

leaf  was  mechanically  stimulated  and  fell  through  58°  in  155 
seconds,  again  stimulated  it  fell  through  37°  in  114  seconds, 
again  stimulated  it  fell  through  16°  in  85  seconds,  and  on 
fourth  stimulus  it  fell  through  9  °  in  69  seconds.  It  thus  swept 
through  an  arc  of  120°  in  little  more  than  7  minutes,  but  as  I 
have  since  proved,  by  shortening  the  time  intervals  between 
stimuli,  the  same  movement  can  be  got  in  less  than  half 
the 'period.  The  average  rate  of  expansion  is  from  12-15 
minutes  in  the  first  three  species  now  under  consideration,  but 
under  certain  conditions  may  be  only  7-9.  Ice  and  ice-water, 
hot  water  and  dry-heat  stimuli,  alcohol,  ether,  etc.,  are  all 
irritants.  6  ^  ether  when  placed  not  merely  at  the  base  of  a 
leaflet  but  even  in  the  middle  of  it,  excites  to  movement. 

I  have  already  referred  to  the  fact  that  Cassia  nictitanSy 
though  closely  resembling  Mimosa  pudica  in  its  leaf  move- 
"ments,  shows  a  greatly  reduced  capacity  for  propagation  of 
stimuli  from  one  leaflet  or  pair  of  leaflets  to  another.  The 
four  species  now  under  consideration  are  still  less  sensitive  in 
this  respect,  for  it  is  possible  to  make  a  terminal  or  lateral 
leaflet  fall  through  38°-67°  without  participation  of  the  other 
two  leaflets  in  the  change. 

Desmodiiim  rotjindifoliuin  is  the  least  sensitive  of  the  genus, 
for  in  its  sluggish  action  and  limited  amplitude  of  movement 
(amounting  to  io°-2  5°)  it  more  nearly  resembles  some  of  the 
Lespedezas.  Now  Ainphicarpcea,  Dcsmodimn  cajiesceiis,  and 
Dcsmodinm  panicidatiim  are  all  upright  growers,  and  are 
therefore  exposed  in  their  leaflets  to  the  full  effects  of  night 
cold  and  heat  radiation  from  the  tissues,  and  I  believe  that 
this  may  largely  explain  why  in  evolutionary  development  they 
have  become  much  superior  to  Dcsmodinm  rotmidifoliimiy  whose 
long  sucker-like  shoots  run  along  the  ground,  and  give  off 
leaflets  that  nestle  amongst  surrounding  herbage. 

AmpJiicarpcea^  Dcsmodinm  and  Lcspcdcza  all  seem  to  resemble 
the  species  of  Oxalis,  and  to  differ  from  such  as  Mimosa 
p7idica  or  Cassia  nictitans  in  that  the  primary  stalk  of  the  leaf 
does  not  appear  to  move,  or  only  moves  so  slightly  that  it 
has  hitherto  escaped  my  observation.  But  this  difference  is 
secondary  and  not   fundamental,   I   believe,   for   in   two   such 


IRRITO-CONTRACTILITY  IN  PLANTS.  203 

closely  related  species  as  Mimosa  piidica  and  Mimosa  hipulina, 
the  former  has  the  most  rapid  motion  in  its  leaf  stalk  at  present 
known,  the  latter  seems  to  be  quite  stationary. 

It  may  now  be  asked,  How  do  the  seed  leaves  of  sensitive 
plants  behave  ?  De  Candolle  first  noticed  that  the  cotyledons 
of  Mimosa  are  irritable  to  touch,  while  Bert,  Pfeffer  and 
Darwin  have  confirmed  his  observations.  To  the  last  writer, 
also,  we  owe  a  list  of  additional  plants  with  sensitive  cotyledons, 
for  he  pointed  out  that  several  species  of  Oxalis,  Mimosa^ 
Trifoliicm,  Cassia  and  Lotus  all  show  sleep  movenients,  and 
further  that  eight  species  of  Cassia,  a  species  of  Smit/iia, 
Mimosa  piidica  and  Mimosa  sensitiva,  also  Oxalis  sensitiva, 
are  irritable  to  contact.  I  have  not  only  been  able  to  add 
several  to  Darwin's  list,  but  have  learned  much  as  to  their 
extreme  sensitiveness.  Various  of  them  are  not  merely  irritable 
to  a  single  impact,  but  undergo  a  definite  amount  of  contraction 
that  varies,  as  in  the  vegetative  leaves,  with  age  and  environ- 
ment. They  contract  to  their  fullest  extent  with  a  summation 
of  stimuli,  they  are  highly  irritable  to  heat  and  cold  stimuli, 
also  to  chemical  agents  that  excite  contractile  tissue. 

Those  of  the  sensitive  plant  are  most  active  during  the 
period  that  their  activity  is  of  greatest  benefit,  viz.,  in  the 
very  young  state  (seedlings  2-10  days  old),  since  their  great 
function  is  to  protect  the  first  leaves  and  growing  bud.  When 
the  latter  have  pushed  out  above  the  cotyledonary  tips,  the  pro- 
tective function  has  ceased,  and  their  irritable  movements  are 
greatly  lost.  This,  of  course,  is  owing  to  the  protoplasm 
becoming  senile,  for  as  their  irritability  becomes  less  their 
green  color  is  transformed  into  yellow,  and  they  then  shrivel 
and  soon  after  drop  off.  This  may  have  misled  Darwin  into 
supposing  that  the  seed  leaves  of  Mimosa  piidica  were  feebly 
sensitive,  for  he  speaks  of  their  rising  after  irritation  by 
rubbing,  or  by  tapping  for  from  30  seconds  to  3  minutes, 
but  I  cannot  understand  why  he  considered  so  much  effort 
necessary,  unless  it  be  that  he  happened  to  choose  rather 
old  seedlings  or  experimented  at  low  temperatures. 

The  irritable  movements  of  the  cotyledons  as  compared  with 
the  foliage  leaves  of  Oxalis  dendroides  are  of  great  importance. 


204  BIOLOGICAL   LECTURES. 

Some  botanists  have  attempted  to  distinguish  between  plants 
that  show  a  heat-sleep  with  the  leaflets  directed  upwards,  and 
a  night-sleep  in  which  they  fall  down,  as  compared  with  others 
that  have  the  same  position  alike  in  heat  and  sleep.  But  here 
is  a  plant  which  folds  upwards  its  seed  leaves,  and  downwards 
its  foliage  leaves  under  all  kinds  of  stimuli. 

In  such  a  condensed  statement  as  I  now  give,  it  would  be 
impossible  to  dwell  on  the  anatomical  details  of  the  species 
already  named.  Suffice  it  that  they  all  exhibit  beautiful 
intercellular  protoplasmic  unions  from  cell  to  cell,  as  was  first 
demonstrated  for  the  sensitive  plant  by  Gardiner. 

We  may  now  attempt  shortly  to  answer  the  question,  How 
are  the  irrito-contractile  movements  originated  and  propagated, 
and  what  are  the  cell  changes  which  accompany  them  .'*  Until 
within  the  last  decade,  botanists  were  compelled  to  view  living 
vegetable  cells  as  organic  units  that  were  sharply  demarcated 
from  each  other  by  cellulose  walls,  and  whose  life  phenomena 
were  due  to  protoplasmic  activity  of  each  cell.  But  no  matter 
how  complex  and  intricate  the  chemical  changes  that  were 
effected,  they  still  viewed  the  protoplasm  as  a  rather  watery 
substance  of  no  great  consistency,  tenacity,  or  structural 
complexity.  The  study  of  nuclear  changes  during  new  cell 
formation,  of  the  existence  of  sensitive  movements  in  different 
plants,  but  especially  the  demonstration  of  intercellular  proto- 
plasmic threads  that  link  together  the  cell  protoplasms  into 
one  harmonized  body,  compel  us  to  accept  the  conclusion  that 
the  protoplasm  of  a  vacuolated  cell  is  a  very  complex  and 
resistant  substance  that  is  extremely  responsive  to  environ- 
mental stimuli.  Still,  with  few  exceptions  —  and  chief  among 
these  we  reckon  Gardiner  of  Cambridge  —  botanists  clung, 
and  even  now  cling,  to  the  idea  that  irrito-contractile  move- 
ments are  simply,  or  at  least  chiefly,  due  to  migration  of  cell 
sap  from  a  living  cell  or  cells  into  intercellular  spaces,  owing 
to  contraction  of  the  cellulose  walls.  Sachs,  Bert,  Nageli  and 
Schwendener,  Pfeffer  and  DeVries  have  propounded  the  view 
that  contraction  of  the  walls  is  the  important  factor. 

The  untenableness  of  this  position  is  being  gradually  recog- 
nized,   and    one    can    see    that    a    change    is    coming.     The 


IRRITO-CONTRACTILITY  IN  PLANTS.  205 

aggregation  j^rocess  which  Darwin  first  observed  in  the  cells 
of  Droscra  tentacle  has  been  carefully  studied,  and  is  now 
known  to  be  due  to  expulsion  of  cell  sap  through  the 
protoplasmic  sac  of  certain  cells,  and  that  this  escapes  into 
intercellular  spaces  in  at  least  some  instances,  {e.g.  Mimosa 
pudica),  is  practically  demonstrated  by  Pfeffer's  experiments. 
The  opinion  is  now  being  gradually  accepted  that  irritation  of 
the  lower  region  of  the  pulvinus  causes  a  sudden  exudation  of 
the  cell  sap  through  special  pores  in  the  protoplasmic  sac,  and 
that  this  sap  then  escapes  into  the  intercellular  spaces,  or  to 
the  exterior  if  an  incision  be  made.  As  the  cells  of  the 
upper  pulvinus  region  are  now  more  turgid,  fall  of  the  leaf 
follows.^ 

But  from  Wortmann's  studies  on  PJiycomyccs  and  other 
plants,  it  is  demonstrated  that  irritation  of  any  part  of  a  cell 
causes  the  protoplasmic  sac  to  retreat  from  the  wall  at  the 
irritated  region,  owing  to  extrusion  of  a  quantity  of  the  sap 
that  is  enclosed  within  the  sac.  The  process  of  expansion 
then  would  consist  in  the  gradual  resorption  of  sap  into  the 
contracted  cell.  Many  results  point  to  this  conclusion,  and 
the  fact  that  sensitive  plants  if  starved  in  their  water  supply 
cease  to  be  irritable,  is  in  its  favor. 

I  previously  showed,  however,  for  Dioiicea, — and  have  now 
proved  for  several  other  plants, — that  summation  stimuli  can 
be  given  with  definite  results  ;  also,  that  under  heat  and  cold 
stimuli,  chemical  stimuli,  and  electrical  stimuli,  plant  tissues 
behave  exactly  as  do  the  contractile  tissues  of  animals,  while 
the  rate  of  propagation  of  the  stimulus  is  greater  than  that  in 
various  animal  tissues.  It  may  be  affirmed,  then,  of  many 
plants  that  their  protoplasm   is  irritated  by,  and   responds  to, 

1  Since  writing  the  above  the  author  has  observed  a  striking  change  to  occur  in 
the  leaflet  pulvini  of  Mimosa  pudica,  M.  lupulina  Schrattkia^aiigttstata,  and  most 
beautifully  in  Mimosa  sensitiva.  After  stimulation  of  a  leaflet,  and  toward  the 
close  of  the  latent  period  a  sudden  flush  travels  centrifugally  across  the  surface 
of  the  pulvinus.  Immediately  thereafter  the  leaflet  contracts,  and  the  pulvinus 
previously  of  a  whitish  hue  assumes  a  dull  greenish  aspect.  The  author  has 
grounds  for  believing  that  this  is  due  to  migration  of  liquid  into  the  upper  region 
of  the  pulvinus,  and  corresponds  to  a  similar  change  in  a  girdle  of  tissue  above 
the  swollen  leaf  pulvinus,  which  is  possibly  the  area  referred  to  by  Lindsay  nearly 
seventy  years  ago. 


2o6  BIOLOGICAL   LECTURES. 

mechanical,  thermal,  luminous,  chemical  and  electrical  stimuli, 
and  that  the  degree  of  contraction  is  proportioned  to  the  rela- 
tive molecular  activity  of  the  protoplasm  and  the  strength  or 
continuity  of  the  stimulus. 

Accepting  this  position,  I  venture  to  think  that  we  can 
harmonize  many  movements  that  appeared  superfluous  or  dis- 
tinct from  each  other.  It  may  be  asked,  —  and  indeed  has 
been  asked  by  Darwin, — Why  are  plants  that  are  nyctitropjc 
and  parathermotropic  often  very  sensitive  to  impact,  though 
apparently  deriving  no  benefit  from  impact  sensitivity  1  We 
reply  that,  being  sensitive  to,  or  irritated  by,  light,  heat,  or 
cold,  they  must  of  necessity  be  also  sensitive  to  impact, 
even  though  deriving  no  benefit  therefrom,  since  contraction- 
sensitivity  involves  response  to  all  forms  of  energy.  But  let 
us  be  cautious  in  assuming  that  no  benefit  is  got  from  a 
certain  movement  unless  such  benefit  is  patent  to  us.  Sachs 
says  about  the  sensitive  plant,  "  So  far  as  I  am  aware,  no  one 
has  attempted  an  explanation  of  the  use  of  the  irritability  of 
the  leaves  of  Mimosa;  but  I  believe  that  I  am  able  to  afford 
one  ;  for  I  have  often  had  opportunities  of  observing  that  after 
a  severe  hail-storm,  when  plants  of  the  most  various  kinds  — 
and  even  robust  plants,  close  to  my  mimosas,  before  the 
window  or  in  the  open  —  have  been  dashed  and  broken  by 
the  hail-stones,  the  mimosas,  in  spite  of  their  delicate 
structure,  have  come  out  quite  uninjured  ;  a  few  minutes  after 
the  rough  weather  they  expanded  their  leaves  again,  entirely 
unhurt."  He  might  have  added  that  not  merely  from  hail, 
but  from  beating  winds  and  rain,  the  leaves  are  the  better 
protected  ;  as  I  have  proved  for  Mimosa^  Oxalis^  Dcsnio- 
dium,  AmpJiicarpcea^  etc.  As  with  animal  contractile  tissues, 
then,  every  irritable  plant  is  to  a  greater  or  less  degree 
irritable  to  all  forms  of  stimuli.  We  derive  now  from  this  a 
likely  explanation  of  nyctitropic  and  parathermotropic  move- 
ments in  plants.  It  is  universally  recognized  that  every 
species  has  an  optimiim  as  well  as  a  minimum  and  maximum 
temperature  relation.  To  return  to  Oralis  stricta  again,  the 
optimum  during  the  day  is  24°-26°  C,  but  when  it  is  exposed 
to  a  steady  heat-stimulus  from  the  sun's  rays  of  30°-32°  C, 


IRRITO-CONTRACTILITY  IN  PLANTS.  207 

the  protoplasm  will  almost  certainly  contract,  and  the  leaflets 
will  fall.  But  as  evening  advances,  lowering  of  the  air  temper- 
ature, radiation  from  the  leaflets,  —  and  still  more  importantly, 
I  believe,  —  the  cutting  off  of  the  light  stimuli  along  with 
reduced  temperature  of  the  soil,  will  all  act  steadily,  and  the 
leaflets,  newly  recovered  from  the  parathermotropic  state,  will 
pass  soon  after  into  the  nyctitropic  state. 

To  distinguish  the  relation  to  altered  environmental  surround- 
ings, we  speak  of  night-sleep  ©r  nyctitropism,  and  heat-sleep  or 
parathermotropism,  but  fundamentally  both  are  due,  we  believe, 
to  one  and  the  same  fundamental  peculiarity  of  the  protoplasm, 
though  we  cannot  stop  here  to  discuss  Briicke's  assertion  of  a 
difference  owing  to  difference  of  tension. 

A  distinct  exception  to  this  principle,  however,  seemed  to  be 
involved  in  Pfeffer's  statement  first  made  in  \{\?>  Pflaiiz en  physi- 
ologic, and  afterwards  extended  into  a  paper  published  in  his 
Laboratory  Journal .  He  there  asserted  that  sensitive  plants  like 
Mimosa,  Oxalis,  Dioncea,  etc.  differed  fundamentally  from  such 
stem  or  leaf  parts  as  tendrils  and  from  the  hairs  of  Drosera, 
in  that  the  former  were  sensitive  to  impact,  the  latter  only  to 
contact.  So  many  cases  of  summation  of  stimuli  being  needed 
to  effect  movement  had  been  met  with  by  me,  that  I  deter- 
mined to  ascertain  experimentally,  whether  coiling  of  a  tendril 
was  not  due  to  a  summation  of  distinct  impacts  combined,  of 
course,  with  circumnutation  of  the  organ.  Fortunately,  I  had 
fine  plants  of  those  he  experimented  on  growing  in  my  garden 
or  within  easy  reach.  Pfeffer  states  that  the  long,  graceful 
tendril  of  Sicyos  —  the  bur  cucumber  —  only  coils  into  a  helix 
if  subjected  to  contact  rubbing.  I  first  selected  a  primary 
tendril  of  EcJiinocystis  lobata,  that  was  5|  inches  long  and 
faintly  incurved  at  its  tip,  as  is  usual.  Thirty  delicate 
mechanical  shocks  were  given  in  series  of  five  at  intervals  of 
10  seconds,  and  spread  over  i^  inches  of  the  tip.  Soon 
after  delivery  of  the  second  five  —  i.e.,  within  25  seconds  — 
there  was  a  distinct  curving  of  the  irritated  region.  In  6 
minutes  the  tendril  had  curved  sharply  through  |  of  a  circle, 
and  in  23  minutes  through  ij  of  a  circle.  It  was  first 
irritated   at    7.21     p.m.,   and   when    examined    i^    hours    later 


208  BIOLOGICAL   LECTURES. 

by  lamplight,  it  was  still  incurved.  Next  morning  it  had 
again  straightened  out.  I  have  often,  and  admiringly, 
repeated  the  experiment  on  primary  and  secondary  tendrils, 
have  varied  the  time-interval  between  the  shocks,  and  have 
varied  the  number  of  shocks  given,  but  they  have  never  failed 
to  respond.  Though  in  a  few  instances  Sicyos  tendrils  did 
not  sensibly  respond  when  given  20  to  30  stimuli,  the  majority 
behaved  like  those  of  Ecliinocystis. 

Thereafter,  a  large  and  vigorous  plant  of  Ciicinnis  maxima, 
was  experimented  with.  Series  of  5  stimuli  at  intervals  of  one 
second  were  given  every  i-  minute,  and  in  6  minutes,  i.e.  after 
60  stimuli,  two  had  incurved  very  distinctly.  After  14  minutes 
one  had  curved  through  |  of  a  circle,  the  other  through  ]. 
Three  of  different  length  and  age  were  then  chosen  with 
essentially  similar  outcome.  The  whole  subject  of  tendril 
movement,  as  viewed  in  the  above  light,  opens  up  a  wide  field 
for  comparative  and  critical  investigation.  Why  not  merely 
elongation  of  cells  but  growth  in  thickness  of  tissue  should 
then  follow  on  the  side  away  from  that  irritated,  is  not  difficult 
to  understand,  in  view  of  De  Vries'  and  Wortmann's  studies  of 
protoplasmic  movement.^ 

Equally  must  I  take  exception  to  Pfeffer's  assertion  that 
Drosera  tentacle  does  not  inflect  after  contact  stimulus. 
Darwin  stated  that  inflexion  usually  took  place  after  three  or 
more  touches,  though  this  is  denied  by  Pfeffer.  I  find  that  if 
the  leaves  of  D.  rotniidifolia,  D.  iiitcrvicdia  or  D.  dichotonia 
are  healthy  and  secreting  their  viscous  juice  freely,  two  stimuli 
with  a  time-interval  between  of  at  least  25  seconds,  causes 
powerful  incurving,  but  only  after  a  latent  period  of  55-70 
seconds.  Few  things  in  the  range  of  plant  life  have  seemed 
so  impressive  as  watching  Drosera  tentacle  after  second  stim- 
ulus. To  know  that,  as  the  seconds  pass  with  apparently 
no  change  in  the  tentacle,  active  though  invisible  molecular 
movement  is  progressing  which  culminates  after  about  60 
seconds  in  a  steady,  sweeping  incurvation  of  the  tentacle  for 

1  McDougall's  experiments  {Bot.  Gazette,  Vol.  XVIII,  1S93)  on  the  stimulation 
and  movements  of  tendrils,  suggest  broad  lines  of  investigation  that  may  yield 
good  results. 


IRRirO-CONTRACTILITY  IN  PLANTS.  209 

65-70  seconds,  is  a  revelation  to  us  of  the  complexity  of  proto- 
plasmic machinery.  Drosera,  then,  like  Dioncea,  moves  only 
after  a  summation  of  at  least  two  stimuli. 

I  cannot  sit  down  without  acknowledging  here  my  great 
indebtedness  to  Mr.  Oliver,  of  the  Washington  Botanic  Garden, 
for  fine  specimens  of  the  rarer  species  experimented  with,  and 
to  my  friend  and  former  student,  Mr.  Aldrich  Pennock,  who 
not  only  threw  open  his  hot-houses  for  my  use,  but  aided  me 
practically  in  many  ways. 


TENTH    LECTURE. 


THE  MARINE  BIOLOGICAL  STATIONS  OF  EUROPE. 

HASH  FORD   DEAN, 

Columbia  College,  New  York. 

Among  European  nations  the  Marine  Laboratory  has  long 
been  recognized  as  an  important  aid  to  the  advancement  of 
biological  studies.  Groups  of  universities,  centralizing  their 
marine  work  in  convenient  localities,  have  caused  the  entire 
coast  line  of  Europe  to  become  dotted  with  stations,  well 
equipped  and  well  maintained.  Societies,  individuals  and  not 
infrequently  governments  contribute  to  their  support. 

Marine  stations  have  become  distributing  centers,  important 
equally  in  every  grade  of  biological  work  or  training.  A 
student,  for  example,  should  he  visit  a  small  university  in  the 
interior  of  France,  would  receive  his  first  lessons  aided 
by  material  sent  regularly  from  Roscoff  or  Banyuls  :  —  he 
would  examine  living  sponges,  pennatulids,  heroes,  hydroids, 
Loxosoma,  Comatula,  Amphioxus.  Or,  at  Munich,  remote 
from  the  coast,  as  in  the  laboratory  of  Prof.  Richard  Hertwig, 
he  is  enabled  by  means  of  material  from  Naples  to  demonstrate 
the  larval  characters  of  ascidians,  or  the  fertilization  processes 
of  the  sea-urchin.  During  his  winter  studies  the  marine 
station  would  thus  provide  him  with  the  best  material  — 
sometimes  preserved  and  well  fixed,  sometimes  living,  to  be 
prepared  according  to  his  wants.  In  summer  it  affords  him 
the  best  opportunities  to  see  and  collect  his  study  types,  without 
physical  discomforts  and  with  the  greatest  economy  of  time. 
To  the  investigator  the  station  has  become,  in  the  broadest 
sense,  a  university.  He  may  there  meet  the  representative 
students  of  far  and  wide,  fellow-workers  perhaps  in  the  very 


212  BIOLOGICAL   LECTURES. 

line  of  his  own  research,  and  must  himself  unknowingly  teach 
and  learn.  He  finds  out  gradually  of  recent  work,  of  technical 
methods  which  often  happen  most  pertinent  to  his  needs. 
He  carries  on  his  work  quietly  and  thoroughly  ;  his  works  of 
reference  are  at  hand  ;  he  has  the  most  necessary  comforts  in 
working,  and  is  untroubled  by  the  rigid  hours  of  demonstrations 
or  lectures.  The  station,  becomes,  in  short,  a  literal  emporium, 
cosmopolitan,  bringing  together  side  by  side  the  best  workers 
of  many  universities,  tending,  moreover,  to  make  their  observa- 
tions upon  the  best  material  sharper  by  criticism,  most  fruitful 
in  results.  It  has  often  been  remarked  how  large  a  proportion 
of  recently  published  researches  was  dependent,  directly  or 
indirectly,  upon  marine  laboratories. 

A  brief  account  of  the  more  important  of  these  stations 
should  not  prove  lacking  in  suggestions  ;  especially  as  in 
America  the  work  of  the  marine  laboratory  is  often  imperfectly 
understood.  Its  aims  have  been  associated  popularly  with 
those  of  practical  fish  culture  ;  and  even  among  the  trustees 
of  universities  a  disposition  has  often  been  to  regard  an  annual 
subscription  for  a  work  place  in  a  summer  school  as  among  the 
little  needed  expenditures  of  a  biological  department.  So  little 
important  has  a  marine  station  seemed  that  the  greatest 
difficulties  have  ever  been  encountered  to  ensure  the  support 
of  an  American  table  at  Naples, —  although  it  was  well  known 
how  large  a  number  of  our  investigators  were  each  year 
indebted  to  foreign  courtesy  for  the  privileges  of  this  station. 

General  interest  in  the  advancement  of  pure  science  has  in 
Europe  become  a  prominent  feature  of  the  past  decade,  and 
there  can  be  no  doubt  of  the  importance  that  has  come  to  be 
attached  to  studies  bearing  upon  the  problems  of  life,  evolution, 
heredity.  Nor,  at  the  same  time,  does  it  appear  that  matters 
relating  to  practical  fisheries  have  in  any  way  lost  their  interest 
or  support.  To  these,  on  the  contrary,  the  rise  of  pure  biology 
has  often  given  important  aids.  What  has  appeared  abstract 
theory  to-day  has  often  been  converted  into  practice  to-morrow. 
And  even  so  ardent  a  partisan  of  pure  biology  as  Prof, 
de  Lacaze-Duthiers  does  not  hesitate  to  urge  this,  as  sufificiently 
important  in  general  argument,  to  vindicate  the  governmental 


MARINE   BIOLOGICAL   STATIONS   OF  EUROPE. 


213 


support  of  the  laboratories  of  Roscoff  and  Banyuls.  "  Facts 
have  been  found  at  every  step  of  science  which  were  valueless 
at  their  discovery,  but  which,  little  by  little,  fell  into  line  and 
led  to  applications  of  the  highest  importance  —  how  the  obser- 
vation of  the  tarnishing  of  silver  or  the  twitching  leg  of  the 
frog  was  the  origin  of  photography  or  telegraphy  —  how 
the  purely  abstract  problem  of  spontaneous  generation  gave 
rise  to  the  antiseptics  of  surgery." 


^■~^- 


.^  SOLOVETSKAIA 


UNIV.iCHRrlSTlANlA^        ^^^r-T 


r'sEBASTOPOL  ^^ 


As  a  preface  to  the  present  discussion  the  general  number 
and  location  of  the  European  marine  stations  might  conven- 
iently be  indicated  in  the  accompanying  outline  map. 


I.  —  France. 

The  extended  sea-coast  has  ever  been  of  the  greatest  aid  to 
the  French  student  —  along  the  entire  northern  coast  the 
channel  is  not  unlike  our  Bay  of  Fundy  in  the  way  it  sweeps 
the  waters  out  at  the  lunar  tides.  The  rocks  on  the  coast  of 
Britany,  massive  bowlders,  swept  and   rounded  by  the  rushing 


2  14  BIOLOGICAL   LECTURES. 

waters,  will  at  these  times  become  exposed  to  a  depth  as  great 
as  forty  feet.  This  is  the  harvest-time  of  the  collector;  he  is 
enabled  to  secure  the  animals  of  the  deep  with  his  own  hand, 
to  take  them  carefully  from  the  rocky  crevices  where  they  would 
ever  have  avoided  the  collecting  dredge.  From  earliest  times 
this  region  has  not  unreasonably  been  the  field  of  the  naturalist. 
It  was  here  that  Cuvier,  during  the  Reign  of  Terror,  made 
his  studies  on  marine  invertebrates  which  were  to  precede 
his  Rhgjic  Animal.  The  extreme  westernmost  promontories  of 
Brittany  have,  for  the  last  half-century,  been  the  summer 
homes  of  de  Quatrefages,  Coste,  Audouin,  Milne-Edwards  and 
de  Lacaze-Duthiers.  Coste  created  a  laboratory  at  Concarneau, 
but  this  has  come  to  be  devoted  to  practical  fish  culture,  and 
is,  at  the  present  day,  of  little  scientific  interest.  It  is  owing 
to  the  exertions  of  Professor  de  Lacaze-Duthiers  of  the 
Sorbonne,  that  the  two  governmental  stations  of  biology  have 
since  been  founded.  The  first  was  established  at  Roscoff,  in 
one  of  the  most  attractive  and  favorable  collecting  regions  in 
Brittany,  and  has  continued  to  grow  in  importance  for  the  last 
twenty  years.  As  this  station,  however,  could  be  serviceable 
during  summer  only,  it  gave  rise  to  a  smaller  dependency  of 
the  Sorbonne  in  the  southernmost  part  of  France,  on  the 
Mediterranean,  at  Banyuls,  which  had  the  additional  advantage 
of  a  Mediterranean  fauna. 

To  these  French  stations  should  be  added  that  of  Professor 
Giard,  at  Wimereux  near  Boulogne,  in  the  rich  collecting 
funnel  of  the  Straits  of  Dover;  that  of  Professor  Sabatier  at 
Cette,  not  far  from  Banyuls,  a  dependency  of  the  University  of 
Montpelier;  that  of  Marseilles,  and  the  Russian  station  at  Ville- 
Franche,  near  the  Italian  frontier.  An  interesting  station  in 
addition,  is  that  at  Arcachon  near  Bordeaux,  founded  by  a  local 
scientific  society.  Smaller  stations  are  not  wanting,  as  at  the 
Sables  d'Olonne. 

At  Roscoff  the  laboratory  building  looks  directly  out  upon 
the  channel.  In  its  main  room  on  the  ground  floor,  work 
places  are  partitioned  off  for  a  dozen  investigators;  this  on  the 
one  hand  leads  to  a  large  glass-walled  aquarium  room,  seen  in 
the  accompanying  figure,  while  on  the  other  opens  directly  to 


MARINE   BIOLOGICAL   STATIONS   OF  EUROPE. 


215 


adjoining  buildings  which  include  lodging  quarters,  a  well- 
furnished  library  and  a  laboratory  for  elementary  students. 
Surrounding  the  building  is  an  attractive  garden  which  gives 
one  anything  but  a  just  idea  of  the  barrenness  of  the  soil  of 
Brittany.  From  the  sea  wall  of  the  laboratory  one  looks  out 
over  the  rocks  that  are  becoming  exposed  by  the  receding  tide. 
A  strong  enclosure  of  masonry  serves  as  a  vivierXo  be  used  for 


Marine  Station  at  Roscoff,  Brittany. 
(From  photograph,  July,  1891.) 

experiments  as  well  as  to  retain  water  for  supplying  the 
laboratory.  The  students  are,  in  the  main,  those  of  the  Sor- 
bonne,  and  under  the  direction  of  Dr.  Prouho,  their  uiaitre  de 
conferences.  They  are  given  every  opportunity  to  take  part  in 
the  collecting  excursions,  frequently  made  in  the  laboratory's 
small  sailing  vessels,  among  the  rocky  islands  of  the  neighbor- 
ing coast.  Strangers,  too,  are  not  infrequent,  and  are 
generously    granted    every    privilege   of    the    French    student. 


2l6 


BIOLOGICAL   LECTURES. 


Liberality  is  one  of  the  characteristic  features  of  Roscoff.  The 
stranger  who  writes  to  Professor  de  Lacaze-Duthiers  is  accorded 
a  work  place  which  entitles  him  gratuitously  to  every  privilege 
of  the  laboratory  —  his  microscope,  his  reagents,  even  his 
lodging-room  should  a  place  be  vacant.  It  seems,  in  fact,  to 
be  a  point  of  pride  with  Professor  Lacaze  that  the  stranger 
shall  be  welcomed  to  Roscoff,  and  upon  entering  the  laboratory 


Roscoff.     Inierior  of  Aquarium  Room. 
(July,  1891.) 

for  the  first  time,  feel  entirely  at  home.  He  finds  his  table  in 
order,  his  microscope  awaiting  him,  and  the  material  for  which 
he  had  written  displayed  in  stately  array  in  the  glass  jars  and 
dishes  of  his  work  place.  So,  too,  he  may  have  been  assigned 
one  of  the  large  aquaria  in  the  glass  aquarium  room  —  massive 
stone-base  stands,  aerated  by  a  constant  jet  of  sea  water. 

He  finds  a  surprising  wealth  of  material  at   Roscoff,  and  his 
wants  are  promptly  supplied. 


MARINE   BIOLOGICAL    STATIONS   OF  EUROPE. 


17 


At  Banyuls,  the  second  station  pf  the  Sorbonne,  the  build- 
ings are  less  imposing  than  those  of  Roscoff.  It  is  a  plain, 
three-story  building  facing  the  north,  at  the  edge  of  the  prom- 
ontory which  shelters  the  harbor  at  Banyuls.  The  vivicr  is  in 
front  of  the  station,  behind  is  a  reservoir  cut  in  the  solid  rock 
—  receiving  the  waters  of  the  Mediterranean  and  distributing 
it  throughout  the  building.  On  the  first  floor  is  a  large 
aquarium  room  lighted  by  electricity,  well-supplied  with  tanks 


siiHi  I 


fStIi  I 


French  Marine  Station  at  Banyuls-Sur-Mer. 
(October,   1891.) 


and  decorated  not  a  little  with  statuary  donated  by  the 
Administration  of  the  Beaux-Arts.  The  bust  of  Arago 
occupies  an  important  place,  as  the  laboratory  has  been  named 
in  his  honor.  A  suit  of  a  diver  sugests  the  different  tactics  in 
collecting  made  necessary  by  the  slightly  falling  tides  of  the 
Mediterranean.      The   wealth    of   living   forms   in   the   aquaria 


2l8 


BIOLOGICAL    LECTURES. 


shows  at  once  by  variety  of  bright  colors  the  richness  of 
southern  fauna.  Sea  lilies  are  in  profusion;  and  are  gathered 
at  the  very  steps  of  the  laboratory.  The  work-rooms  of  the 
students  are  on  the  second  floor,  equipped  in  a  manner  similar 
to  those  of  Roscoff.  The  director  of  this  station  is  Dr.  Frederic 
Guitel.  It  is  usual  during  the  holidays  at  fall  or  winter,  for  the 
entire  classes  of  the  Sorbonne  to  spend  several  days  in 
collecting-trips    in    the    neighborhood.     The    region,   with   its 


Banyuls-Sur-Mer.     Interior  of  Aquarium  Room. 
(October,   1891.) 

little  port,  is  famous  for  its  fisheries,  and  one  in  especial  is  that 
of  the  Angler,  LopJiiiis,  a  fish  that  would  not  be  regarded  as 
especially  dainty  on  our  side  of  the  Atlantic. 

The  station  on  the  Straits  of  Dover,  at  Wimereux,  has 
earned  a  European  reputation  in  the  work  of  Professor  Giard. 
It  is  but  a  small  frame  building,  scarcely  large  enough  to 
include  the  advanced   students  selected    from  the    Sorbonne. 


MARINE   BIOLOGICAL    STATIONS   OF  EUROPE.        219 

The  laboratory  is,  in  a  way,  a  rival  of  Roscoff,  and  it  is 
noteworthy  that  its  workers  seem  to  make  a  point  of  studying 
the  laboratory  methods  of  the  German  universities. 

The  marine  laboratory  of  Arcachon,  one  of  the  oldest  of 
France,  was  built  in  1867  by  the  local  scientific  society,  and 
was  carried  on  independently  until  the  time  of  the  losses  of  the 
Franco-Prussian  War.  Its  management  was  then  fused  with 
that  of  the  faculty  of  medicine  of  Bordeaux,  with  whose  assist- 
ance, aided  by  that  of  a  small  subsidy  from  the  government, 
the  work  of  the  institution  is  carried  on.  Arcachon,  near 
Bordeaux,  is  in  itself  a  most  interesting  locality.  It  has  become 
a  summering  place,  noted  for  its  pine  lands  and  the  broad,  sandy 
plage,  picturesque  in  summer  with  swarms  of  quaintly-dressed 
children,  the  local  head-dress  of  the  peasant  mingling  with  the 
latest  toilets  from  Paris.  Here  and  there  is  to  be  seen  that 
accompaniment  of  every  French  watering  place,  the  goat  boy 
in  smock  and  berret,  fluting  to  his  dozen  charges  who  walk 
in  a  stately  way  before  him.  The  Bay  of  Arcachon  is  a 
small,  tranquil,  inland  sea,  long  known  for  its  rich  fauna.  In 
large  part  it  is  laid  out  in  oyster  parks,  which  constitute  to  no 
small  degree  the  source  of  wealth  of  the  entire  region.  .  Shal- 
low and  warm  waters  seem  to  give  the  marine  life  the  best 
conditions  for  growth  and  development.  The  laboratory  is 
placed  just  at  the  margin  of  the  water.  It  includes  a  dozen  or 
more  work  places  for  investigators,  well  supplied  with  aquaria, 
a  library  on  the  second  floor,  a  small  museum  containing  col- 
lections of  local  fauna,  including  numerous  relics  of  Cetaceans 
that  have  found  their  way  into  this  inland  sea.  A  small 
aquarium  room,  opened  to  the  public,  is  well  provided  with 
local  forms  of  fishes,  and  like  that  of  Naples,  is  eagerjy  visited. 
Those  who  are  entitled  freely  to  the  use  of  the  work  places  are 
instructors  in  French  colleges,  members  of  the  Society,  and  all 
the  advanced  students  from  the  colleges  of  the  State.  For 
other  students,  work  place  is  given  upon  the  payment  of  a  fee 
whose  amount  is  regulated  each  year  by  the  trustees.  As  at 
Roscoff,   material   is  plentifully  supplied. 

The  Zoological  Station  at  Cette  is  a  direct  annex  of  the 
University  of   Montpelier,  and  it  will  be  gladly  learned  that 


220  BIOLOGICAL   LECTURES. 

its  temporary  building  is  being  replaced  by  one  of  stone, 
which  will  enable  Professor  Sabatier  to  add  in  no  little  way  to 
the  working  facilities  of  his  students.  The  region,  in  every 
essential  regard,  is  similar  to  that  of  Banyuls. 

The  station  at  Marseilles  is  devoted  in  great  part  to  ques- 
tions relating  to  the  Mediterranean  fisheries,  and  owes,  in  a 
measure,  its  financial  support  to  this  practical  work. 

The  station  at  Ville-Franche  is  essentially  Russian.  An 
account  of  this  with  figures  has  recently  been  published 
(Russian  text)  in  Cracow.  The  station  itself  is  well  known 
through  the  work  of  Dr.  Bolles  Lee,  and  it  is  here  that 
Professor  Carl  Vogt  has  been  a  constant  visitor. 

II.  —  England. 

The  laboratory  at  Plymouth  is  quite  a  recent  one,  its 
foundation  due  in  the  first  instance  to  the  efforts  of  Professor 
Ray  Lankester.  Its  building,  first  opened  in  1888,  is,  in  many 
regards,  hardly  second  to  Naples.  This  locality  was  found 
well-suited  for  the  needs  of  an  extensive  marine  station. 
Opposite  Brittany  it  takes  advantage  of  the  same  extremes  of 
tide,  and  the  rocky  Devonshire  coast  affords  one  of  the  richest 
collecting  grounds.  The  situation  of  the  building  is  a  remark- 
able one;  it  stands  at  one  end  of  the  ancient  Hoe  of  Plymouth 
—  a  broad,  level  park  whose  high  situation  looks  far  off  over 
the  channel.  At  the  rear  of  the  building  are  the  old  fortifica- 
tions of  the  town.  As  shown  in  the  adjoining  figure,  the 
building  is,  at  the  ends,  three-storied.  On  the  ground  floor  is 
the  general  aquarium  room,  well-supplied  with  local  marine 
fauna,  and  open  to  the  public.  The  laboratory  proper  is  upon 
the  second  floor,  divided  into  eleven  compartments,  the  work 
places  of  the  students.  A  series  of  small  tanks  passes  down 
the  middle  of  the  room.  In  the  western  end  are  the  library, 
the  museum,  the  chemical,  photographic,  and  physiological 
rooms  :  in  the  eastern  are  the  living  quarters  of  the  director. 
The  water  supply  of  the  laboratory  is  contained  in  two  small 
reservoirs  directly  between  the  building  and  the  fortifications, 
and  is  carried  throughout  the  building  by  gas  engines.     Tidal 


MARINE   BIOLOGICAL    STATIONS   OF  EUROPE. 


221 


aquaria  are  in  constant  use  for  developmental  studies.      The 
collecting  for  the  laboratory  is  aided  by  a  38-foot  steam  launch. 

The  present  support  of  the  station  is  not,  unfortunately,  as 
generous  a  one  as  might  be  desired.  The  station  is  obliged  to 
consider  in  the  work  of  its  director  matters  relating  to  public 
fisheries,  and  is  only  enabled  by  this  means  to  secure  govern- 
mental assistance.  The  building  itself  was  constructed  by  the 
efforts  of  the   Marine    Biological   Association   of  the    United 


British  Marine  Laboratory,  Plymouth. 
(August,  1892.) 


Kingdom,  under  whose  auspices  the  present  work  is  being 
carried  on.  The  investigators'  tables  are  occupied  by  any 
founder  of  the  Association,  or  his  representative,  by  the  natu- 
ralist or  institutions  who  have  rented  them.  The  subscription 
price  per  year  of  an  investigator's  place  is  £,^0,  but  tables  may 
be  leased  for  as  short  a  time  as  a  month.      The  laboratory  pro 


22  2  BIOLOGICAL   LECTURES. 

vides  material  for  investigation  and  the  ordinary  apparatus  of 
the  marine  laboratory,  excluding  microscopes  and  accessories. 
The  use  of  the  larger  tanks  of  the  main  aquarium  is  also  per- 
mitted to  the  working  student.  The  work  of  the  laboratory 
includes  investigation  of  fishery  matters,  the  preservation  of 
animals  to  supply  the  classes  of  zoology  in  the  universities 
and  the  formation  of  type  collections  of  the  British  marine 
fauna.  The  naturalist  of  this  station  has  been,  for  a  number 
of  years,  Mr.  J.  T.  Cunningham,  whose  experiments  upon  the 
hatching  of  the  Sole  have  here  been  carried  on. 

Other  British  marine  stations  are  those  of  Liverpool  and  St. 
Andrews,  northeast,  and  Dunbar,  southeast,  of  Edinburgh. 
The  work  of  these  stations  is  only  in  part  purely  biological  ; 
the  practical  matters  of  fisheries  must  be  considered  to  insure 
financial  support.  In  addition  to  these  is  to  be  mentioned  a 
station,  recently  equipped,  on  the  Isle  of  Man.  Still  another, 
most  favorable  in  its  locality,  has  been  established  in  the 
Channel    Isands. 

At  St.  Andrews,  Professor  Macintosh  has  studied  the  ques- 
tions relating  to  the  hatching  and  development  of  the  North 
Sea  fishes.  Its  situation  upon  the  promontory  leading  into 
the  Firth  of  Forth  seems  to  have  been  especially  favorable 
for  the  study  of  the  North  Sea  fauna  —  the  locality,  moreover, 
is  far  enough  northward  to  include  a  numer  of  boreal  forms. 
The  importance  of  St.  Andrews  is  at  length  better  recognized, 
and  a  substantial  grant  from  the  government  will  enable  a 
large  and  permanent  marine  station  to  be  here  constructed. 
The  facilities  for  work  have,  up  to  the  present  time,  been 
somewhat  primitive,  —  a  simple  wooden  building,  single-storied, 
has  been  partitioned  off  into  small  rooms,  a  general  laboratory, 
with  work  places  for  half  a  dozen  investigators,  a  director's 
room,  aquarium,  and  a  small  out-lying  engine  house  with 
storage  tanks.  To  the  laboratory  belongs  a  small  sail-boat  to 
assist  in  the  work  of  collecting. 


MARINE   BIOLOGICAL    STATIONS   OF  EUROPE.        223 

III.  —  Holland. 

Holland,  in  the  summer  of  1890,  opened  its  zoological 
station  in  the  Helder,  a  locality  which,  for  this  purpose,  had 
long  been  looked  upon  with  the  greatest  favor.  There  is  here 
an  old  town  at  the  mouth  of  the  Zuyder  Zee,  the  naval  strong- 
hold of  Holland,  a  station  favorable  for  biological  work  on 
account  of  the  rapid-running  current  renewing  the  waters  of 


Dutch  Zoological  St.uion   ai    ihk  IIkldkr. 
(Fig.  from  Tijdschr.  d.  Ned.  Dierk.  Vereen.  5  Juli,  1S90.) 

the  Zee.  The  station  was  founded  by  the  support  of  the 
Zoological  Society  of  the  Netherlands,  whose  valuable  work 
by  the  contributions  of  Hubrecht,  Hoek,  and  Horst,  has  long 
been  known  in  connection  with  the  development  of  the  oyster 
industry  of  Holland.  The  work  of  the  Society  had  formerly 
been    carried   on    by  means   of    a   portable    zoological    station 


224 


BIOLOGICAL   LECTURES. 


which  the  investigators  caused  to  be  transplanted  to  different 
points  along  the  East  Schelde,  favorable  on  account  of  their 
nearness  to  the  supplies  of  spawning  oysters.  The  present 
station  at  the  Helder  is  situated  directly  adjoining  the  great 
Dyke,  a  small  stone  buiding,  two  stories,  surrounded  by  a 
small  park,  as  seen  in  the  adjacent  figure.  In  itself  the  labo- 
ratory is  a  model  one,  —  the  rooms  are  carefully  finished,  and 
every  arrangement  has  been  made  to  secure  working  conven- 
iences. A  large  vestibule  leads  directly  into  two  laboratory 
rooms,  and,  by  a  hallway,  communicates  with  the  large,  well- 
lighted  library  and  the  rooms  of  the  director.  The  aquarium 
room  has,  for  convenience,  been  placed  in  a  small  adjacent 
building.  The  director  of  this  station  is  Professor  Hoek,  and 
the  President  of  the  Society  is  Professor  Hubrecht. 

IV.  — Naples. 

The  Stazione  Zoologica  at  Naples  during  the  past  twenty 
years  has  earned  its  reputation  as  the  center  of  marine  bio- 
logical work.  Its  success  has  been  aided  by  the  richness  of 
the  fauna  of  the  Gulf,  but  is  due  in  no  small  degree  to 
careful  and  energetic  administration.  The  director  of  the 
station.  Professor  Dohrn,  deserves  no  little  gratitude  from 
every  worker  in  science  for  his  untiring  efforts  in  securing  its 
foundation  and  systematic  management.  Partly  by  his  private 
generosity  and  partly  by  the  financial  support  he  obtained,  the 
original  or  eastern  building  was  constructed.  Its  annual  main- 
tenance was  next  assured  by  the  aid  he  obtained  throughout 
(mainly)  Germany  and  Austria.  By  the  leasing  of  work  tables 
to  be  used  by  the  representatives  of  universities,  a  sufficient 
income  was  maintained  to  carry  on  the  work  of  the  station 
most  efficiently.  A  gift  by  the  German  government  of 
a  small  steam  launch  added  not  a  little  to  the  collecting 
facilities. 

Attractiveness  is  one  of  the  striking  features  of  the  Naples 
station.  It  has  nothing  of  the  dusty,  uncomfortable,  gloomy 
air  of  the  average  university  laboratory.  Its  situation  is  one 
of  the  brightest  ;  it  has  the  gulf  directly  in  front,  about  it  the 


MARINE   BIOLOGICAL    STATIONS   OF  EUROPE. 


225 


city  gardens,  rich  in  palm  trees  and  holm  oaks.  The  building 
itself  rises  out  of  beds  of  century  plant  and  cactus  like  a  white 
palace  ;  the  fashionable  drive-way  alone  separates  it  from  the 
water's  edge.  In  full  view  is  the  Island  of  Capri,  to  the  east- 
ward is  Vesuvius,  —  a  bright  and  restful  picture  to  one  who 
leaves  his  work  for  a  five  minutes'  stroll  on  the  long,  covered 
balcony  which  looks  out  over  the  sea. 


The  Stazione  Zoologica  at  Naples. 
(May,  1892.) 


The  student,  in  fact,  knows  the  Naples  station  before  he 
visits  it,  although  he  can  hardly  anticipate  the  busy  and 
profitable  stay  that  there  awaits  him.  He  has  received  the 
circular  from  the  Secretary  of  the  laboratory  while  perhaps  in 
Germany,  when  he  secured  the  privilege  of  a  table.  He  is 
told  of  the  best  method  of  reaching  Naples,  the  precautions  he 
must  take  to  secure  the  safe  arrival  of  his  boxes  and  instru- 


2  26  BIOLOGICAL   LECTURES. 

ments.  He  is  told  to  send  directions  as  to  the  material  he 
desires  for  study  ;  he  is  notified  of  the  supplies  which  will  be 
allowed  him,  and  of  the  matters  of  hotels,  lodging,  and  bank- 
ing, necessary  even  to  a  biologist.  At  the  first  sight  of  the 
building  he  is  impressed  most  favorably,  and  it  is  not  long 
before  he  comes  to  look  upon  his  work-place  as  his  particular 
home,  open  to  him  day,  night,  and  holiday.  He  likes  the  gen- 
eral air  of  quietness  —  in  no  little  way  significant  of  system  in 
every  branch  of  the  station's  organization  ;  his  neighbors  are 
friendly,  and  he  feels  that  even  the  attendants  are  willing, 
often  anxious  to  give  him  help. 

At  present  the  station  at  Naples  consists  of  two  buildings  ; 
the  first,  shown  in  the  foreground  in  the  accompanying  figure, 
is  the  older,  the  main  building  ;  behind  it  is  the  newly  built 
physiological  laboratory.  In  the  basement  of  the  main 
building  is  the  aquarium,  well  managed,  open  to  the  public,  and 
eagerly  visited.  Passing  into  the  aquarium  room  from  the 
main  entrance,  one  descends  into  a  long,  dark,  concreted  room, 
lighted  only  through  wall-tanks  brilliant  on  every  side  with  the 
varied  forms  of  life.  There  are  in  all  about  two  dozen  large 
aquaria  embedded  in  the  walls  of  the  sides  and  of  the  main 
partition  of  the  room.  The  water  is  clear  and  blue.  The 
background  in  each  aquaria,  built  of  rock  work,  catches  the 
light  from  above  and  throws  in  clear  relief  the  living  inmates. 
The  first  tank  will  perhaps  be  full  of  star  fish  and  sea  urchins, 
bright  in  color,  often  clustered  on  the  glass  each  with  a  dim 
halo  of  pale,  thread-like  feet.  In  the  background  may  be  a 
living  clump  of  crinoids,  flowering  out  like  a  garden  of  bright- 
colored  lilies.  In  a  neighboring  tank,  rich  with  dark-colored 
seaweeds,  will  be  a  group  of  flying  gurnards,  reddish  and 
brilliantly  spotted,  feeling  cautiously  along  the  bottom  with  the 
finger-like  rays  of  their  wing-shaped  fins.  Here,  too,  may  be 
squids,  delicate  and  fish-like,  swimming  timidly  up  and  down  ; 
perhaps  a  series  of  huge  triton  snails  below  amid  clustered 
eggs  of  cuttle  fish.  In  another  tank  would  be  a  bank  of  sea 
anemones  with  all  the  large  and  brilliant  forms  common  to 
southern  waters.  Here  maybe  corals  in  the  background  and  a 
forest  of  sea  fans  in  orange,  red  and  yellow,  with  a  precious 


MARINE   BIOLOGICAL    STATIONS   OF  EUROPE.        227 

fringe  of  pink  coral,  flowering  out  in  yellow  star-like  polyps. 
There  may  again  be  a  host  of  ascidians,  delicate,  transparent, 
solitary  forms,  the  lanky  Ciona,  the  brilliantly  crimson  Cynthia 
and  huge  masses  of  varied,  compound  forms.  Swimming  in 
the  water  may  be  chains  of  Salpa  and  occasionally  a  number 
of  Amphioxus,  the  latter,  as  they  from  time  to  time  emerge 
from  the  sandy  bottom,  flurry  about  as  if  with  sudden  fright, 
quickly  to  disappear.  Variety  is  one  of  the  striking  characters 
of  neighboring  tanks.  In  one,  brilliant  forms  will  outvie  the 
colors  of  their  neighbors  ;  in  another,  the  least  obtrusive 
mimicry  will  be  exemplified.  The  stranger  has  often  to  examine 
carefully  before,  in  the  seemingly  empty  tank,  he  can  determine 
on  every  side  the  living  forms  whose  color  characters  screen 
them  effectively.  Thus  he  will  see  sand-colored  rays  and 
flounders,  the  upturned  eyes  of  the  curious  star-gazer  almost 
buried  in  the  sand,  a  series  of  mottled  crustaceans  wedged  in 
a  rocky  background,  an  occasional  crab  wandering  cautiously 
about,  carrying  a  protective  garden  of  seaweeds  on  his  broad 
back  ;  odd  sea  horses  posing  motionless  mimicing  the  rough 
stems  of  the  seaweeds.  In  the  larger  tank  sea  turtles  float 
sluggishly  about  ;  and  coiled  amid  broken  earthern  jars  are 
the  sharp-jawed  murrys,  suggestive  of  Roman  dinners  and  of 
the  cultural  experiments  of  Pollio.  Aeration  in  the  aquaria 
is  secured  effectively  by  streams  of  air  which  are  forced  in  at 
the  water  surface  and  subdivide  into  bright  clouds  of  minute 
silvery  bubbles.  The  tanks  are  cared  for  from  the  rear  passage- 
ways ;  attendants  are  never  seen  by  visitors,  and  constant 
attention  has  given  the  aquaria  a  well  earned  reputation.  Well 
illustrated  catalogues  in  French,  German,  English  and  Italian 
enable  the  stranger  to  better  appreciate  the  aquarium. 

To  the  remainder  of  the  building  strangers  are  not  admitted. 
A  marble  stairway  leads  from  the  door  of  the  aquarium  to  a 
loggia  which  opens  into  the  territory  of  the  students.  A  long 
pathway  of  grating  extends  across  the  open  center  of  the 
building, —  whose  skylight  top  admits  the  light  to  the  aquarium 
below.  On  the  one  hand  is  the  main  laboratory  room,  on 
the  other  the  library  and  separate  rooms  intended  for  more 
fortunate  investigators.     One  enters  the  main  laboratory,  passes 


228  BIOLOGICAL   LECTURES. 

a  wall  of  student  aquaria  and  sees  a  series  of  alcoves  formed 
by  low  partitions,  each  work-place  with  its  occupant,  his 
apparatus,  his  books,  his  jars  —  altogether  often  a  picture  not 
of  the  utmost  tidiness.  A  small  iron  staircase  leads  to  a 
gallery  which  gives  a  second  tier  of  work  places  and  doubles 


The  Library  of  the  Naples  Station. 
(June,  1892.) 

the  working  capacity  of  the  room.  Here,  side  by  side,  will  be 
representative  workers  from  universities  of  every  country  of 
Europe. 

The  library  room  adds  not  a  little  to  the  attractiveness  of 
the  Naples  station.      It  is  a  long  room,  and,  as   shown   in  the 


MARINE   BIOLOGICAL    STATIONS   OF  EUROPE.        229 

figure,  is  adorned  with  frescoes  in  a  truly  Italian  style.  It 
looks  out  into  a  long  loggia  with  view  of  the  sea  and  Capri, 
where  the  student  is  wont  to  retire  in  after  luncheon  hour 
with  easy-chair  and  book.  The  working  library  is  of  the 
best  and  is  sure  to  contain  the  results  of  the  most  recent 
researches.  The  desk  shown  in  the  figure  is  one  on  which 
each  day  is  to  be  found  the  latest  publications.  In  the 
upper  pigeon-holes  are  the  cards  prepared  for  each  investigator 
on  his  advent  to  Naples  ;  with  these  he  replaces  the  volumes 
which  he  has  taken  to  his  work  place.  Every  division  of  the 
laboratory  is  carefully  organized  and  is  under  the  charge  of  a 
special  assistant.  Prof.  Hugo  Eisig,  the  assistant  director,  has 
taken  the  welfare  of  each  student  under  his  personal  charge, 
and  it  is  not  until  the  end  of  his  stay  that  the  visitor  recognizes 
how  much  has  been  done  for  him. 

There  is  no  more  interesting  department  of  the  station 
than  that  of  receiving  and  distributing  the  material.  Its 
headquarters  is  in  the  basement  of  the  physiological  laboratory, 
and  here  Cav.  Lo  Bianco  is  to  be  found  busy  with  his  aids 
and  attendants  amid  a  confusion  of  pans,  dishes  and  tables, 
encountering  the  Neapolitan  fishermen  who  have  learned  to 
bring  all  of  their  rarities  to  the  station.  The  specimens  are 
quickly  assorted  by  the  attendants  ;  such  as  may  not  be  needed 
for  the  immediate  use  of  the  investigators  are  retained  and 
prepared  for  shipment  to  the  universities  throughout  Europe. 
The  methods  of  killing  and  preserving  marine  forms  have  been 
made  a  most  careful  study  by  Lo  Bianco,  and  his  preparations 
have  gained  him  a  world-wide  reputation.  Delicate  jelly-fish 
are  to  be  preserved  distended,  and  the  frail  forms  of  almost 
every  group  have  been  successfully  fixed.  The  methods  of  the 
Naples  station  were  kept  secret  only  until  it  was  possible  to 
verify  and  improve  them,  as  it  was  not  deemed  desirable  to 
have  them  given  out  in  a  scattered  way  by  a  number  of 
investigators. 

Lo  Bianco  has  made  the  best  use  of  the  rich  material  passing 
daily  through  his  department,  and  has  been  enabled  to  prepare 
the  most  valuable  records  as  to  spawning  seasons  and  as  to 
larval  conditions.      He  knows  the  exact  station  of  the  rarest 


230  .     BIOLOGICAL   LECTURES. 

species,  and  it  seems  to  the  stranger  a  difficult  matter  to  ask 
for  a  form  which  cannot  be  directly  or  indirectly  procured.  It 
adds  no  little  to  the  time  saving  of  the  student  to  find  each 
morning  at  his  work  place  the  fresh  material  which  he  has 
ordered  the  day  before,  and  there  is  usually  an  embarrassment 
rather  than  a  dearth  of  riches. 

A  collecting  trip  often  occurs  as  a  pleasant  change  from  the 
indoor  work  of  the  investigator.  An  excursion  to  Capri  may 
be  planned  ;  the  launch  will  be  brought  to  the  quay  near  the 
station  and  the  party  will  embark.  The  collecting  tubs  are 
soon  scattered  over  the  deck  and  filled  with  the  dredge 
contents.  Some  of  the  passengers  are  quickly  at  work  sorting 
out  their  material,  one  seizing  brachiopods,  another  compound 
ascidians,  another  sponges.  Others  will  wait  until  the  surface 
nets  have  been  brought  in  and  the  contents  turned  into  jars. 
All  will  depend  upon  Lo  Bianco  as  an  appellate  judge  in 
matters  of  identification. 

Many  Americans  have  availed  themselves  of  the  privileges 
of  Naples  and  the  former  lack  of  support  of  an  American 
table  needs  little  comment.  Of  those  who  have  hitherto 
visited  Naples  more  than  three-quarters  have  been  indebted 
to  the  courtesies  of  German  universities.  At  present  of  the 
two  American  tables  one  is  supported  by  the  Smithsonian 
Institution,   the  other  by  gift  of  Mr.   Agassiz. 

The  entire  Italian  coast  is  so  rich  in  its  fauna  that  it  is  due, 
perhaps  only  to  the  greatness  of  Naples,  that  so  few  stations 
have  been  founded.  Messina  has  its  interesting  laboratory  well 
known  in  the  work  of  its  director.  Professor  Kleinenberg.  The 
Adriatic,  especially  favorable  for  collecting,  has  at  Istria  a 
small  station  on  the  Dalmatian  coast,  and  at  Trieste  is  the 
Austrian  station. 

V.  —  Trieste. 

Trieste  possesses  one  of  the  oldest  and  most  honored  of 
Marine  Observatories,  although  its  station  is  but  small  in 
comparison  with  that  of  Naples,  Plymouth  or  Roscoff.  Its 
work  has  in  no  small  way  been  limited  by  scanty  income;  it 
has  offered  the  investigator  fewer  advantages  and  has  there- 


MARINE   BIOLOGICAL    STATIONS 


OF  EUROPE.        231 


fore  become  outrivalled.  During  a  greater  part  of  the  year  it 
is  but  little  more  than  the  supply  station  of  the  University  of 
Vienna,  providing  fresh  material  for  the  students  of  Professor 
Claus.  Its  percentage  of  foreign  investigators  appears  small; 
its  visitors  are  usually  from  Vienna  and  of  its  university. 

Trieste  is  in  itself  a  small  but  busy  city,  growing  in  active 
commerce.  Its  quays  are  massive  and  bristle  with  odd-shaped 
shipping  of  the  Eastern  Mediterranean.     Its  deep  and  basin- 


The  Station  at  Trieste. 


like  harbor  affords  a  collecting  ground  as  rich  as  the  Gulf  of 
Naples. 

The  station  has  been  located  at  a  quiet  corner  of  the  harbor, 
just  beyond  the  edge  of  the  lighthouse.  Its  building  is  some- 
what chalet-like,  situated  on  a  small,  well-wooded  knoll,  as  seen 
in  the  adjacent  figure.  About  it  are  trellis-covered  grounds 
enclosed  by  high  walls,  and  separated  from  the  harbor  only  by 
the  main  roadway  of  the  quays.      One  enters  the  laboratorv 


232 


BIOLOGIC  A  L   LEC  TURKS. 


garden  through  a  large  gateway  and  passes  into  a  court-yard 
whose  outhouses  disclose  the  pails  and  nets  of  the  marine 
laboratory.  Perhaps  an  attendant  will  here  be  sorting  out  the 
plunder  which  a  bronze-legged  fisherman  has  just  brought  in. 

A  library  and  the  rooms  of  the  director,  Dr.  Graeffe,  are 
close  by  the  entrance  of  the  building.  In  the  basement  is  the 
aquarium  room,  —  somewhat  dark  and  cellar-like  ;  its  tanks 
small  and  shallow,  their  inmates  representing  especially  stages 
of  Adriatic  hydroids  and  anthozoans.  On  the  second  story  are 
the  investigators'  rooms,  — large,  well-lighted,  looking  out  over 
garden  and  sea.  Near  by  is  a  museum  of  local  fauna,  rich  in 
crustaceans  and  in  the  larv^al  stages  of  Adriatic  fishes. 

VI-IX.  —  Germany,   Norway,   Sweden,   Russia. 

The  German  universities  have  contributed  to  such  a  degree 
to  the  building  up  of  the  station  at  Naples  that  they  have 
hitherto  been  little  able  to  avail  themselves  of  the  more  con- 
venient but  less  favorable  region  of  German  coasts.  The 
collecting  resources  of  the  North  Sea  and  of  the  Baltic  have 
perhaps  been  not  sufficiently  rich  to  warrant  the  establish- 
ment of  a  central  station.  On  the  side  of  the  Baltic,  the 
University  of  Kiel,  directly  on  the  coast,  may  itself  be  regarded 
as  a  marine  station.  At  present  the  interest  in  founding  local 
marine  laboratories  has,  however,  become  stronger.  The  newly 
acquired  Heligoland  has  become  the  seat  of  a  well-equipped 
Governn%ental  station.  The  island  has  been  long  known  as 
most  favorable  in  collecting  regions,  and  its  position  in  the 
midst  of  the  North  Sea  fisheries  gives  it  especial  importance. 

Its  present  building  is  three-storied,  of  stone,  situated  near 
the  water  on  the  Jutland  side  of  the  island.  Work  places  are 
provided  for  four  investigators.  Its  director  is  Dr.  F.  Heinke  ; 
his  assistants,  Drs.  Hartlaub,  Ehrenbaum,  and  Kuckuck.  The 
Istrian  laboratory  at  Rovigno,  a  favorable  collecting  point  on 
the  Adriatic,  is  to  be  included  among  the  German  stations  It 
was  destined  by  Dr.  Hermes,  its  founder,  as  the  supply  depot 
of  the  Berlin  aquarium.  Of  its  work  places,  two  have  been 
rented  by  the  Prussian  government,  and  a  third  is  to  be 
obtained  by  application  to  Dr.  Hermes. 


MARINE   BIOLOGICAL    STATIONS   OF  EUROPE.        233 

Norway  like  Germany  is  strengthening  its  interest  in  local 
marine  laboratories.  Two  permanent  stations  have  quite 
recently  been  established,  one  at  Bergen,  —  the  other  at 
Drobak,  a  dozen  miles  south  of  Christiana.  The  former  is 
the  larger,  a  dependency  of  the  Museum  of  Bergen.  It  is 
under  the  charge  of  Dr.  Brunchorst,  —  to  whom  its  founda- 
tion is  due,  —  and  Drs.  Appellof  and  Hansen.  Its  two- 
storied  villa-like  building  provides  work  places  for  eight 
investigators  :  a  well  maintained  aquarium  on  the  first  floor 
is  open  to  the  public.  The  second  and  smaller  station  is 
devoted  almost  exclusively  to  research  in  morphology.  It 
is  a  dependency  of  the  University  of  Christiana  and  is  under 
the  directorship  of  one  of  its  professors,  Dr.  Johan  Hjort. 
With  the  richest  collecting  resources  these  new  stations  may 
naturally  be  expected  to  yield  most  important  results. 

The  Swedish  station  has  long  been  associated  with  the  work 
of  its  late  director,  Professor  Loven.  It  is  situated  on  the  west 
coast  near  the  city  of  Gothenburg.  Its  three  original  buildings, 
a  laboratory  and  two  dwelling-houses,  were  constructed  about 
fifteen  years  ago  by  a  gift  of  Dr.  Regnell  of  Stockholm.  The 
laboratory  is  a  wooden  building  well  furnished  with  aquaria, 
provided  in  its  second  story  with  separate  work  places  for 
investigators.  It  is  at  present  maintained  by  governmental 
subsidy  ;  its  recently  appointed  director  is  Dr.  Hjalmar  Theel 
of  the  State  Museum  at  Stockholm.  Its  students  are  mainly 
from  the  University  of  Upsala  ;  up  to  the  present  time 
foreigners  have  not  been  admitted. 

Russians  have  ever  been  most  enthusiatic  in  marine  research, 
and  their  investigators  are  to  be  found  in  nearly  every  marine 
station  of  Europe.  The  French  laboratory  on  the  Mediterranean 
at  Ville-Franche  is  essentially  supported  by  Russians.  At 
Naples  they  are  often  next  in  numbers  to  the  Germans  and 
Austrians.  The  learned  societies  of  Moscow  and  St.  Petersburg 
have  contributed  in  no  little  way  to  marine  research.  The 
station  at  Sebastopol,  on  the  Black  Sea,  has  become  permanent, 
possessing  an  assured  income.  That  near  the  Convent  Solovet- 
sky,  on  the  White  Sea,  though  small,  is  of  marked  importance. 
It   is   already  in   its   thirteenth   year.      Professor   Wagner,   of 


234  BIOLOGICAL   LECTURES. 

St.  Petersburg,  has  been  its  most  earnest  promoter  as  well  as 
constant  visitor.  He  in  fact  caused  the  Superior  of  the  Convent 
to  become  interested  in  its  work  and  secured  a  permanent 
building  by  the  Convent's  grant  ;  he  was  then  enabled  by  an 
appropriation  from  the  government  to  provide  an  equipment. 
Its  annual  maintenance  is  due  to  the  Society  of  Naturalists  of 
St.  Petersburg.  The  matter  of  the  appointment  of  a  perma- 
nent director  for  the  summer  months  is  now  being  agitated  by 
him.  The  station  Solovetskaia  is  said  to  possess  the  richest 
collecting  region  of  the  Russian  coasts.  It  is  certainly  the 
only  laboratory  which  has  at  its  command  a  truly  Arctic 
fauna. 


APPENDIX 


THE   WORK    AND    THE    AIMS    OF    THE    MARINE 
BIOLOGICAL    LABORATORY. 

C.  O.  WHITMAN. 

The  Marine  Biological  laboratory  of  Wood's  HoU  combines  the 
functions  of  a  research  laboratory  with  those  of  a  school.  While  it 
differs  thus  from  the  marine  laboratories  of  Europe,  it  may  also 
be  said  to  take  a  somewhat  exceptional  position  among  American 
sea-side  laboratories,  both  in  its  organization  and  its  scope  of  work. 
It  supplements  the  work  of  the  biological  departments  of  the  schools 
and  colleges,  and  at  the  same  time  serves  as  a  scientific  centre  for 
investigation.  It  provides  not  only  for  general  courses  of  study 
in  zoology  and  botany,  but  also  —  what  is  of  quite  exceptional 
importance -^-T^^r  technical  training  preparatory  to  im'estigation  and 
special  instruction  and  guidance  for  beginners  in  investigation.  It  is 
this  advanced  instruction  that  makes  the  school  tributary  to  the  side 
of  original  investigation,  in  which  the  work  and  the  aims  of  the 
laboratory  centre.  Research  is  the  dominating  function  of  the 
laboratory  ;  instruction  is  merely  a  means  to  this  end. 

Although  the  laboratory  is  wholly  free  from  government  control,  it 
is  truly  national  in  organization  and  aims.  It  is  governed  by  a  board 
of  trustees,  on  which  the  leading  colleges  and  universities  of  the 
country  are  represented.  Its  officers  of  instruction  and  investigation 
have  been  drawn  from  no  less  than  fifteen  educational  institutions, 
and  its  membership  has  extended  to  one  hundred  and  thirty-one 
colleges,  universities,  seminaries,  academies,  schools  and  laboratories. 

From  the  beginning  of  this  undertaking  it  has  been  clearly  seen 
that  the  realization  of  its  aims  depended  largely  on  securing  the  general 
support  of  the  colleges,  and  the  active  cooperation  of  all  who  were 
interested  in  the  foundation  of  a  national  marine  station.  To  secure 
these    ends    the  clearly  defined   aims   of   the  laboratory  were  made 


236  APPENDIX, 

known  as  widely  as  possible,  and  the  invitation  for  united  action  was 
extended  to  institutions  and  investigators  throughout  the  country. 
The  result  is  that  during  the  last  session  the  following  eighteen 
institutions  subscribed  for  rooms  and  tables  : 

Bowdoin  College,  Missouri  Botanical  Garden, 

Brown  University,  Mt.  Holyoke  College, 

Bryn  Mawr  College,  Nortliwestern  University, 

Chicago  University,  Princeton  College, 

Cincinnati  University,  Rochester  University, 

Columbia  College,  Smith  College, 

Hamilton  College,  Vassar  College, 
Massachusetts  Institute  of  Technology,      Wellesley  College, 

Miami  University,  Williams  College. 

To  this  list  may  be  added  the  American  Association  for  the 
Advancement  of  Science,  as  its  subscription  for  next  year  has  been 
announced. 

During  the  same  session  forty-one  investigators  were  at  work  at 
the  laboratory,  thirty-three  of  whom  occupied  private  rooms,  while 
the  rest  had  tables  in  the  general  laboratories  for  beginners  in 
investigation.  The  whole  number  of  students  and  investigators 
was  one  hundred  and  eleven,  representing  seventy-two  colleges, 
universities  and  schools,  and  no  less  than  seventeen  states. 

To  those  who  by  word  and  example  have  encouraged  cooperation, 
this  record  will  certainly  be  gratifying  ;  and  perhaps  it  will  be 
accepted  by  all  as  an  assurance  that  good-will  and  united  effort  have 
not  been  fruitless.  For  six  years  the  Marine  Biological  Laboratory 
has  stood  for  the  first  and  the  only  cooperative  organization  in  the 
interest  of  Marine  Biology  in  America.  Gradually  it  has  come  to 
ba  understood  that  the  creation  of  such  an  organization  was  a  step 
in  the  right  direction.  An  important  need  was  felt  and  there  was 
but  one  way  to  meet  it.  That  way  was  cooparative  action.  It  was 
clearly  seen  that  the  Government  could  not  be  expected  to  undertake 
the  work.  An  independent  foundation  was  needed  and  one  removed 
from  all  danger  of  sectional  domination.  The  effort  to  reach  such 
a  foundation  through  a  cooperative  organization  was  no  menace  to 
any  existing  laboratory.  Time  has  shown  that  the  laboratory  was 
not  an  unneeded  creation.  It  is  no  longer  necessary  to  search  "  the 
by-ways  and  hedges  "  for  investigators,  but  our  buildings  have  to 
be  extended  every  year  or  two  in  order  to  provide  room  for  them. 
Each  summer  now  sees  a  conjiress   of  biolo2:ists  assembled   at  the 


APPENDIX. 


237 


laboratory,  and  every  new  comer  learns  the  value  of  scientific 
fellowship. 

Had  the  Marine  Biological  Laboratory  done  nothing  beyond  the 
creation  of  a  sound  cooperative  organization,  it  would  at  least  have 
fulfilled  one  all-essential  part  of  its  mission.  That  it  has  done,  and 
so  effectively  that  it  is  not  likely  to  be  undone. 

The  record  of  the  laboratory  as  a  scientific  station  is  shown  in  the 
following  list  of  works  : 

PAPERS   PUBLISHED. 
H.  Ayers. 

A  Contribution  to  the  Morphology  of  the  Vertebrate  Head.     ZooL 

Anz.,  1890. 
On  the  Origin  of  the  Internal  Ear  and  the   Functions  of  the  Semi- 
circular Canals  and  Cochlea.     Milwaukee,  1890. 
Concerning  Vertebrate  Cephalogenesis.  Joiirn.of  Morph.^YV,  1890. 
The    Ear    of    Man  ;    its    Past,    its    Present,  and    its   Future.    Btoi. 

Lectures,  I,  Boston,  1890. 
Die  Membrana  tectoria,  was  sie  ist,  und  die  Membrana  basilaris,  was 

sie  verrichtet.     Anai.  Anz.^  VI,  1891. 
A  Contribution  to  the   Morphology  of  the  Vertebrate   Ear,  with    a 

Reconsideration  of  its  Functions.    Journ.  of  Morph.,  VI,  Nos. 

I  and  2,  1892. 
The  Macula  Neglecta  again.     Anat.  Anz.^  VIII,  1893. 
Ueber   das    peripherische    Verhalten    der    Gehornerven    und    den 

Werth  der  Haarzellen  des  Gehororgans.     Anat.  Anz.,  VIII, 

1893. 
The  Auditory  or  Hair-cells  of  the  Ear  and  their  Relations  to  the 

Auditory  Nerve. ,  Journ.  of  Morph.,  VIII,  1893. 
Bdellostoma  dombey.     Biol.  Lectures^  II,  1893. 

H.  C.  BuMPUS. 

The    Embryology  of    the  American   Lobster.     Journ.  of  Morph., 

V,  1 891. 
A  New  Method  in  the  Use  of  Celloidin.     Atner.  Nat.,  1892. 
A  Laboratory  Course  in  Invertebrate  Zoology.     Providence,  1892. 

Cornelia  M.  Clapp. 

Some  Points  in  the  Development  of  the  Toad-fish  (Batrachus  Tau). 
Journ.  of  Morph.,  V,  1891. 

E.  G.  CONKLIX. 

'  The  Cleavage  of    the  Ovum  in   Crepidula  fomicata.     ZooL  Anz.y 
No.  391. 
The  Fertilization  of  the  Ovum.     Biol.  Lectures,  II,  1893. 


238  APPENDIX. 

Bradley  M.  Davis. 

Development  of  the  Frond  of  Champia  parvula,  Harv.,  from  the 
Carpospore.  Annals  of  Botany^  Vol.  VIj  No.  24,  Dec, 
1892. 

E.  G.  Gardiner. 

Weismann  and  Maupas,  on  the  Origin  of  Death.  Biol.  Lectures 
1,1890. 

J.  E.  Humphrey. 

Notes  on  Technique.     Botanical  Gazette.,  XV,  7,  1 890. 

E.  O.  Jordan. 

The  Habits  and  Development  of  the  Newt.  Journ.  of  Morph.^ 
Vol.  VII,  No.  2,  1893. 

J.  S.  KiNGSLEY. 

The   Ontogeny  of    Limulus.     Preliminary.     Zool.  Anz.,    No.   345, 

1890,  and  Amer.  Nat.^  1890. 
The  Embryology  of  Limulus.    Jotirn.  of  Morph.,  Vol.  VII,  No.  i, 

and  Vol.  VIII,  No.  2. 
The    Marine    Biological    Laboratory.      Popular  Science   Monthly, 

Sept.,  1892. 

Frederic  S.  Lee. 

Ueber  den  Gleichgewichtssinn.     Centralblatt  fiir  Physiologie.,  1892. 

Wm.  Libbey,  Jr. 

The  Study  of  Ocean  Temperatures  and  Currents.  Biol.  Lectures., 
I,  1890. 

F.  R.  Lillie. 

Preliminary  Account  of  the  Embryology  of  Unio  complanata. 
fourn.  of  Morph., 'Vl\l,l>^o.  T,,  i^c)2,. 

Wm.  a.  Locy. 

The. Formation  of  the  Medullary  Groove,  and  Some  Other  Features 

of  Embryonic  Development  in  the  Elasmobranchs.    Journ.  of 

i^^r/y^..  Vol.  VIII,  No.  2. 
The  Optic  Vesicles  in  Elasmobranchs  and  their  Serial  Relation  to 

Other  Structures  on  the  Cephalic  Plate.     Journ.  of  Morph.., 

Vol.  IX,  No.  I,  1893. 

Jacques  Loeb. 

Ueber    kiinstliche    Umwandlung    positiv  heliotropischer  Thiere    in 

negativ  heliotropische  und  umgekehrt.     Pfluger''s  Archiv  fur 

Physiologic,  Bd.  LIV. 
A  Contribution  to  the  Physiology  of  Coloration  in  Animals.    Journ. 

^/J/^r/>^.,  Vol.  VIII,  1893. 
Investigations  in  Physiological  Morphology,  3.    Journ.  of  Morph., 

Vol.  VII. 


APPENDIX.  239 

Ueber    die    Entwicklung    von    Fischembryonen    ohne     Kreislauf. 

Pfluger's  Archiv,  Bd.  LV. 
On  some  Facts  and  Principles  of  Physiological  Morphology.     Biol. 

Lectures,  II,  1893. 

J.    MUIRHEAD    MACFARLANE. 

Irrito-Contractility  in  Plants.     Biol.  Lectures,  II,  1893. 
E.  L.  Mark. 

Polychoerus  caudatus,   nov.   gen.    et    nov.   spec.     Festschrift  zum 
siebenzigste7i  Geburtstage  Rudolf  Letickarts,  Leipzig,  1892.. 

T.  H.  Morgan. 

The.  Relationships  of  the  Sea  Spiders.     Biol.  Lectures,  I,  1892. 

A  Contribution  to  the  Ontogeny  and  Phylogeny  of  the  Pycnogonids. 

Johns  Hopkins  Studies,  Vol.  V,  No.  i,  1891. 
The  Test-cells  of  the  Ascidians.    Journ.  of  M or  ph.,  V,  1891. 
The  Growth  and  Metamorphosis  of  Tornaria.    Journ.  of  Morph., 

Vol.  V,  No.  2,  1892. 
Spiral  Modification  of  Metamerism.    Journ.  of  Morph.,  Vol.  VII, 

No.  2,  1892. 
Balanoglossus  and  Tornaria  of  New  England.     Zool.  Anz.,   No. 

407,  1892. 
Experimental  Studies  on  Teleost   Eggs.     Anat.  Anz.,  Vol.  VIII, 

No.  2,  1893. 

J.    P.   McMURRICH. 

Contributions   on   the    Morphology   of    the    Actinozoa.      (2)    The 

Embryology  of  the  Hexactiniae.    Journ.  of  Morph.,  Vol.   IV, 

1890. 
Contributions  on  the  Morphology  of  the  Actinozoa.     (3)  The  Phylo- 
geny of  the  Actinozoa.    Journ.  of  M or  ph.,  Vol.  V,  1891. 
The  Development  of  Cyanea  arctica.     Amer.  Nat.,  XXV. 
The  Gastrasa  Theory  and  its  Successors.     Biol.  Lectures,  I,  1890. 
The  Formation  of  the  Germ-layers  in  the  Isopod  Crustacea.     Zool. 

Anz.,  No.  397,  1892. 
Julia  B.  Platt. 

Contribution  to  the  Morphology  of  the  Vertebrate  Head.    Journ.  of 

Morph.,  Vol.  V,  1 89 1. 
The    Anterior    Head-cavities  of  Acanthias.     Zool.  Anz.,   No.  344, 

May,  1S90. 
Further  Contributions  to  the  "Morphology  of  the  A'ertebrate  Head. 

Atiat.  Anz.,  Vol.  VI,  pp.  251. 

H,    F.    OSBORX. 

Evolution  and  Heredity.     Biol.  Lectures,  \,  i%C)0. 
John  A.  Ryder. 

Dynamics  in  Evolution.     Biol.  Lectures,  II,  1893. 


240 


APPENDIX. 


W.  A.  Setchell. 

Preliminary  Notes  on  the  Five  Species  of  Doassansia  Cornu.     Proc. 

Amer.  Acad.,  XXVI,  1891. 
An  Examination  of  the  Species  of  the  Genus  Doassansia  Cornu. 
Annals  of  Botany,  VI,  1892. 

Louise  B.  Wallace. 

The  Structure  and  Development  of  the  Axillary  Gland  of  Batrachus. 
Journ.  of  Morph.,  Vol.  VIII,  No.  3,  1893. 

S.  Watase. 

On  Caryokinesis.     Biol.  Lectures,  I,  1890. 

The    Origin  of   the    Sertoli's    Cell   (abstract).     Amer.  Nat.,   May, 

1892. 
On  the   Significance  of  Spermatogenesis  (abstract).     Amer.  Nat., 

July,  1892. 
On   the    Phenomena   of    Sex-Differentiation,      fourn.    of  Morph., 

Vol.  VI,  No.  3,  1892. 
Homology  of  the  Centrosome.    fourn.  of  Morph.,  Vol.  VIII,  No. 

2,  1893. 

Herbert  J.  Webber. 

On    the   Antheridia  of    Lomentaria.     Annals  of  Botany,   Vol.   V, 
April,  1 891. 

Wm.  M.  Wheeler. 

A   Contribution  to    Insect  Embryology,    fourn.   of  Morph.,   Vol. 
VIII,  No.  I,  1893. 

W.  P.  Wilson. 

The  Influence  of  External  Conditions  on  Plant  Life.     Biol.  Lectures 
11,  1893. 

E.  B.  Wilson. 

Some  Problems  of  Annelid  Morphology.     Biol.  Lectures,  I,  1890. 
Origin  of   the   Mesoblast-Bands  in   Annelids,    fourn.  of  Morph., 

Vol.  IV,  No.  2,  1890. 
The   Cell-lineage  of    Nereis.     A  Contribution  to  the   Cytogeny  of 

the  Annelid  Body,    fourn.  of  Morph.,  Vol.  VI,  1892. 
The  Mosaic  Theory  of  Development.     Biol.  Lectures,  II,  1893. 

C.  O.  Whitman. 

Specialization  and  Organization.     Biol.  Lectures,  I,  1890. 

The  Naturalist's  Occupation.     Biol.  Lectures,  I,  1890.  " 

The    Inadequacy  of    the  Cell-theory  of    Development,    fourn.  of 

Morph.,  Vol.  VIII,  No.  3,  and  Biol.  Lectures,  II,  1893.   • 
A  Marine  Observatory.     Popular  Science  Monthly,  Feb.,  1893. 
A   Marine  Observatory  the    Prime   Need    of    American    Biology. 

Atlantic  Monthly,  June,  1893. 


APPENDIX.  241 

The  Work  and  Aims  of   the   Marine  Biological   Laboratory.    Biol. 

Lectures.,  II,  1893. 
The  Echinoderm   Egg  and  the  Theory  of   Isotropism.    Journ.  of 

Morph.,  Vol.  IX,  1893. 
The    Metamerism    of    Clepsine.      Festschrift    zum     siebenzigsten 

Geburtstage  Rudolf  Leuckarts.,  Leipzig,  1892. 
A    Sketch    of    the    Structure    and     Development    of    the    Eye    of 

Clepsine.     SpengeVs  Zool.  fahrb.,  VI,  1893. 


PAPERS   IN  PRESS. 

H.  A  VERS. 

The  Relations  of  the  Peripheral   Territory  of  the  Auditory  Nerve 

as  shown  by  Methylen-blue. 
Certain  Facts  and  Theories  in  Modern  Neurology. 

E.  G.  CONKLIN. 

The  Embryology  of  Crepidula.     Part  I.     History  of  the  Cleavage. 

The  Dynamics  of  Fertilization  and  Cleavage. 
Elizabeth  E.  Bickford. 

Experiments  on  Regeneration  and  Heteromorphosis  in  Tubularian 
Hydroids. 
Martha  Bunting. 

The  Origin  of  the  Sex-cells  in  Hydractinia  and  Podocoryne  and  the 
Development  of  Hydractinia.    fourn.  of  M or  ph..,  Vol.  IX,  1894. 
Elizabeth  Cooke. 

On  the  Osmotic  Qualities  of  the  Muscles  of  Marine  Animals. 

E.  G.  Gardiner. 

Early  Development  of  Polychoerus  caudatus. 
Ida  H.  Hyde. 

The  Nervous  Mechanism  of  Respiratory  Movements  in  Limulus. 

F.  S.  Lee. 

A    Study  of  the    Sense  of   Equilibrium    in    Fishes.     I.    fourn.   of 
Physiology. 

D.    J.  LiNGLE. 

On  the  Reversal  of  the  Direction  of  the  Contraction  of  the  Heart 
in  Ascidians. 

Jacques  Loeb. 

Ueber    das    Sauerstoffbediirfniss    des    Embryo    in    verschiedenen 

Entwicklungsstadien. 
Ueber  die  Herstellung  zusammengewachsener  Doppelt-  und  Mehr- 

fachembr)-'onen  by  Seeigeln. 
Ueber  die  Bedeutung  von   Gehirn  und   Auge   fiir   die    Reactionen 

niederer  Thiere  auf  Licht. 


242  APPENDIX. 

A.  D.  Morrill. 

Pectoral  Appendages  and  their  Innervation  in  Prionotus. 
Julia  B.  Platt. 

The    Ontogenetic    Differentiation   of    the    Ectoderm    in    Necturus. 
(Preliminary  Notice.) 
Mary  Schively. 

Ueber  den  Einfluss  der  Concentration  des  Seewassers  auf  die 
Herzthatigheit  einiger  Seethiere.  Pfliiger's  Archiv  fiir 
Physiologic. 

S.  Watase. 

On  the  Nature  of  Cell-Organization.     Biol.  Lectures,  Vol.  II,  1894. 

Wm.  M.  Wheeler. 

Syncoelidium  pellucidum,  a  New  Marine  Triclad.    Journ.  of  Morph. 
Planocera  inguilina,  a  Polyclad  Inhabiting  the  Branchial  Chamber 
of  Sycotypus  Canaliculatus  Gill.    Journ.  of  Morph..,  Vol.  IX, 
1894. 


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